Setting Essay
I wrote one of these before, but figured that it could be clarified a few years later. This is my conception of the Fading Suns setting, in general, and outlines how characters can expect to behave and be treated within their roles.
A New Dark Age
It's 3000 years in our future, but everyone acts like they did 1000 years in our past, right? Not entirely. The setting is a mishmash of cultures and technology, so it's kind of hard to believe that everyone will behave like they did in the middle ages just because feudalism is present. In general, and on most worlds, technology gravitates towards the mid 20th century. This means that most people, even the low-class, have access to reasonably affordable transportation and communication. Further, there's a lot more weird things - 2nd republic or other high tech devices, aliens, and mystic powers - that show up enough to tend to broaden most peoples' mindsets away from the uninterested, close-minded superstition that characterized the original dark ages.
Basically, it's a lot easier to have your character act (and expect others to act) essentially, at root as a modern person with modern sensibilities. That will make it easier to incorporate all the other things that do influence attitudes and actions.
Technology
The fall has made technology a real mishmash in the Known Worlds. Between information theft, loss, and church purges, technology fell to a barely industrial level a few centuries ago, and fear of tech has kept it from growing at anywhere near the original speed. For the vast majority of freemen, standard technology is about 1950s level. That is to say, that all but the most backwards of peasants can assume access to the technological amenities present in the middle of the 20th century (if not, necessarily, the culture or hairstyles). In most cities you'll find peasants with radio, flashlights, trains, hospitals, running water and electricity, pistols and rifles, processed food and goods, and even cars and planes if the rulers don't proscribe freedom of transportation. There are lots of factory officers and minor guild members that know how to produce these goods, and their use is widespread. Only in truly back-water or oppressive locations will you find freemen using pre-industrial tech, though bonded serfs are more likely to be lacking the full list of technological amenities.
On top of this, there's the truly high tech. Remnants from the second republic, alien technologies, and Engineer forward thinking means that the haves are most definately seperated from the have-nots. Those with the freedom, access, and Firebirds can field all sorts of interesting tech: plasma and laser weapons, energy shields, plastic or synth armor, space ships, hovercrafts, fuzion power, cybernetic appendages, genetic modification, instant health-care, computers, and so on. Most of this is cutting edge, stuff that only a handful of highly-trained individuals, mostly guild members, understand fully; there are so few producers that the goods remain uncommon and expensive. Some of it is beyond the cutting edge - remnants of the Second Repubic that can still be made by leftover factories but which can only be fixed by true geniuses that begin to comprehend the tech, but who are powerless to reproduce it.
So on the technology front, assume that mid-20th century gear is the norm, and anything less or more is hard to find except on the extreme ends of society. As PCs with importance and money to burn, you wind up with more access to truly high-tech stuff than most people you meet, but still can only renew your supplies in the rare locations that have the tech to sell to anyone but the ruling elite.
The Nobility
Ah, the nobles, humanity's overlords. To picture what life is like under the nobility, look at modern America. Take the governmental elite, and leave in all of their tendency towards corruption of power, ties to special interest groups, and upbringing without connection to the lower classes. Keeping that, remove the old, boring white men and insert the colorful, interesting, beautiful people of Hollywood in their places, with all of their attitude. Now remove any sense of accountability and term limits. Yes, those are your nobles - vapid, corrupt, power hungry, money grubbing beautiful people who are only answerable to their peers. At least in general.
The nobility is one giant eugenics project. Nobles are more attractive, more healthy, more capable in leadership roles, better trained, better educated, and richer than pretty much anyone else. This makes some people annoyed, some jealous, and other worshipful. That this also tends to lead to mental illness, megalomania, and lack of empathy for the common man is seen as a minor problem for all the advantages gained. Nobles have become an institution, and on paper they have almost unlimited power and freedom to abuse their subjects.
There are three reasons why this doesn't happen. The first is peers: nobles may not have to answer to constituents, but they do have to answer to cousins. A noble that ruins his family's image by being a jerk is going to piss off those family members enough to chastize him, and possibly even worse. If there's one thing celebrities and politicians hate, it's having their approval ratings trashed by something that isn't even their fault. The second reason is the other estates: the church and the guilds also have vested interests in the populace as a whole - abused peasants are less religious, and less likely to spend Firebirds on stuff. The other estates might not be able to do something directly against the nobles, but they can certainly withhold financial and political support if it suits them. The final reason is the potential for uprising: the people as a whole might be willing to take abuse, but there's no telling what their breaking point is. When you're outnumbered many thousands to one, and a significant portion of the population has access to technology that's not terribly greatly trumped by what you've got, the potential for a revolution is scary. Thus, most nobles are going to avoid becoming terribly oppressive if only to keep from being blacklisted by their peers, censured by their rivals, and reviled by their underlings. Obviously, some nobles, like the Decados, can get away with more than others for various reasons.
In short, in practice, in most areas of the Known Worlds the vast majority of people aren't oppressed, but neither does their opinion matter on matters of laws, regulations, and politics. It's rather like the current era, only more obvious, but since the rulers are also the celebrities it seems less restrictive to a lot of people.
The Guilds
Guilds are basically unions expanded to a universal level. Your vast majority of freemen who practice a trade are going to be beholden to a guild, but not necessarily members. Essentially, they pay dues to keep the guilds from running them out of town, but aren't technically members in the "have Benefice conferred rank" sense of the word. Your average factory worker probably takes a small hit on his pay every year because the foreman or factory owner is paying the Engineers, for example, but neither the owner nor the workers are actually considered Engineers. In exchange, the guilds can be expected to give some small manner of protection to those that pay them dues, if only to make sure that the source of revenue doesn't dry up. The presence of guilds is yet another innovation that keeps the known worlds from falling purely into feudalism.
And as a side note, most guild members, even ones with rank, are not heretics. Athiesm and 3rd republicanism are rare, as guild members were raised the same as everyone else, and are generally prone to fitting their later knowledge into their earlier beliefs, rather than vice versa. There is probably a higher tendency towards Deism in the guilds, as increased understanding of the sciences does tend to convince guild members that there isn't an angel pushing every planet, and such. Your run of the mill guild member is going to believe in the Pancreator, and probably in the goodness of His Church, but not really expect that He takes an active role in many things at all.
The Church
The church is a conundrum. In theory, it has pretty much unlimited power over the spirtual and political realms in the known worlds. In theory, all of the church sects believe the same basic things, and can present a unified religious belief based on the Omega Gospels. Theory is often quite different from practice.
In actuality, the church is a morass of beliefs and politics. Having taken in pretty much all the old Urth religions, the sects formed along the many lines where those beliefs didn't line up. Orthodoxy follows more fundamentalist doctrines, trying to consider all the words in the Omega Gospels as Truth, and thus having numerous internal schisms when this is impossible. The Avestites tend towards the beliefs that favor a wrathful, smiting creator, though opinions vary as to whether the Pancreator is a vengeful, fiery deity or simply a loving parent that considers discipline to be important. The Amaltheans tend towards the loving, nurturing god beliefs, yet also take in a lot of the new agey stuff about proper health and the natural form, so can be pretty close minded towards "unnatural" things such as processed chemicals, cyberware, and unions incapable of bearing children. The Brother Battle, like many orders of religious knights, tend to be slack in their actual dogma, tending to believe that a good dose of general, undirected faith is all that's important when their major role is hitting evil with a stick. Finally, the Eskatonics snatched up all the pseudo-religious beliefs and neopagan ideas like a three year old getting candy, often leaving them just a hair short of crossing the line that many consider heresy.
What all this means, is that it's not quite so hard to fit into the seemingly oppressive Universal Church as the corebook's slant might indicate. Most people don't have the dogmatic, Catholic viewpoint unless they're actually patrons of the Orthodoxy. Most people are going to develop their own slant to their beliefs once they get old enough, and join the congregation of a sect that supports that. This is to say, just because someone refuses to attend confession that doesn't mean they're going to hell; their order and church may consider meditation, purification rites, contemplation of Creation/Nature, or private prayer to be more important than confession. This also means that heresy is even harder to pick out - the inquisitors can't just go around flambeing people because they don't go to church. A soldier may follow the brother battle credo and only feel that he needs to go to church after a battle. A doctor may feel that it's much better to do charitable medicine in the community than to waste a couple of hours sitting through service every weekend.
In short, the vast majority of people in the setting are religious, and most can even agree on central religious tenets, but there is enough choice in each of the sects that it's not necessary to treat the Universal Church as the oppressive Catholicism that turns off most of we more secularly minded gamers. You can and should have a character with religious beliefs (whether or not they're conflicted), but you don't have to model those beliefs on the fundamentalist Christianity of the 20th century that seems to often come across in Fading Suns sourcebooks.
This makes the true heretics and demon worshippers even scarier, since they're not just non-Catholic, they're truly following beliefs that nearly anyone on the modern Earth would consider repulsive.
And that's my essay on how I conceive of the setting when I'm running it.