I set up my first fixed-gear bike as a commuter, so it had to have fenders (it rains a lot here). I found that after I put them on I would ride happily in the rain, or after the rain, without worrying about being drenched with dirty water.
I bought a new bike (also fixed) and thought I'd keep it 'cool' and light, and did not put fenders on it. I got caught out in the rain once, got wet and dirty, and promptly went out and bought full fenders.
The h*ll with cool!! I'll take practical any day.