i just went fixed on my langster a couple of days ago. it's kinda hilly where i live so i went to 18t and kept both brakes on cause i didn't want to have to have a bad experience if i bailed and be turned off fixed. i'm trying to ride without ever using the brakes but sometimes the downhills get the best of me. it's a great experience and a great workout. my legs still turn when i'm sitting at my desk at work. and for around thirty bucks for a cog it's not much to lose if you hate it. i think you'll like it though, i feel like i'm in more control of the bike. except when i'm practicing track stands...it may be awhile.
anyway, i'm a noob so take anything i say with a grain of salt. that being said, i don't know if i'm overreacting (and sorry if you feel like i'm highjacking this thread) but none of th lbs's around here are fixie-friendly. all the info i get is on this forum so thanks. anyway, when i went ficed the chainline was just a tad off, onyl enough to visually observe a skew and to make for a noisy grinding ride. the mechs looked at it and said "we've seen worse" and said that this bike like all track bikes aren't good for riding around the city. i asked about a shim for the cog and they said i wouldn't want to lose the precious few threads on the hub and that the only way to adjust it is to adjust the bottom bracket but it wasn't worth it cause i wouldn't be able to adjust it that little. anyway, i guess i'm just overreacting but i'm worried about the uneven wear on the cog and chainring over time. are they right that i shouldn't worry about it? oh, its a surly 1/8 8t, if you're wondering.