Thanks to a raucous, fun session of play on Friday, and the LA's decision that I obviously had enjoyed that enough to make the purchase worthwhile, I picked up a copy of Burning Wheel on Saturday. When I actually got to read the rulebooks, it was initially daunting, but I rapidly picked up the jargon, and I'm now confident I can follow a conversation about it. The system is, at its heart, very simple: roll dice, and count how many are good. Compare that to a target number, and see if you did what you wanted or not.
Other points are: it's a game that rewards characters for attempting, not just succeeding. Didn't make the test? You still learned something. Do that often enough, and you'll get better. This makes a lot more sense than the yar-boo-sucks approach often taken in RPGs, where failing a check is treated as utter, abject failure and you don't even get to learn from your mistakes.
The abstractions are well-chosen - no more micromanagement of finances, you can simply roll using a stat to figure out if you can afford what you want.
Social mechanics. Oh, sweet social mechanics. Normally, this defaults to "loudest and/or most stubborn player wins". Not in Burning Wheel. Thanks to the Duel of Wits, even the quiet guy who only ever speaks when spoken to (that would be me; hi, me!) can win a shouting match in character.
Balance. It's told to go hang. Elves are über, and that's it; Dwarves are über also; humans are not über in anything except possibilities. There's no actual class (you want a mage in armour with a big axe? Sure, if you can persuade the GM to let you take enough lifepaths) but there's a lot of flavour. Character creation is interestingly handled; you choose lifepaths. What this means is that you hve to pick where you were born, how you grew up, and what this left you with. Each lifepath advances your age, gives you skill points and trait points, provides you with a useful skill and usually gives you a trait as well. It also allows you to take other skills and traits at reduced cost. The process of character creation is slow initially (my first character took me about four solid hours to burn) but winds up with a very flavourful person, instead of the usual result of a point-buy system, Fy-Tor Mk. IV (who is identical to Fy-Tors Mk. I-III).
Overall, if you're into roleplaying at all and don't own Burning Wheel, I strongly recommend you go out and buy it. Even if you don't use it, it will make you think about RPGs.