After yesterday's grump-inducing experience at the gym, I'm pretty sure my answer would be:
My favorite thing about Burning Man, though I haven't been yet, is that cell phones will not work there. Having a whole week free from having to hear the 1812 overture done MIDI style, hearing one-sided conversations at the gym, or thinking the other dog walker is talking to me when she's actually talking on her earbud is worth more to me than all the "radical self expression" on the entire Playa. I know there'll still be rave camps and other such unpleasant thumpeta thumpeta, but the fact that I'll be so far away from civilization that I am spared the intrusion of ringtones is enough to make me giddy with excitement.
Also, no lawn in the desert to keep those damn kids off of.