Here's the dirty scoop on what we're really looking for: people who can think of ideas that give us cool ideas on how to interact with them. Characters that feel like they'll be active rather than passive. And you know what does that? It sure ain't fancy long-winded philosophical tracts. That's a misunderstanding that I often see, both in people who apply and people who don't apply because they're afraid they won't measure up to our standards.
A sense of fun. An ability to come up with nifty ideas, and enjoy playing with them.
Length? Excessive length's more common a complaint than excessive briefness. All that matters is that you're good at saying what you're saying. Don't break your back writing The Collected Epic Histories Of The Lost Age Of My Character, or give us Dick And Jane And Spot. Some of the best characters had applications that would fit on one page.
It really does matter that you get along with people well. That you're reasonably adaptable. If you tend to have highly demanding rules and expectations for others' behavior upon you, or if you deal quite poorly with players who don't have styles quite like yours, you aren't very likely to thrive here. We've had players stir up shit, then leave when no one wanted to play with them because of it.
It's okay to be a little goofy. We have a reputation for high-fauntin' artiness, but that's only part of what goes on (and it's the exceptional logs that get posted). We want characters with personality, really. Ones who can make us think shiny thoughts.
Don't stress out on the applications. Just have a good idea of what makes your character interesting and fun.
Check out some past examples of the good ones.