In my experience, if you're going to do a decent amount of miles (for me 30+ a day) on a fixed, in all conditions, then it's a really good idea, provided you get decent quality gear to do it on. I mashed together a road bike gear bike with pretty crap components and I had problem after problem.
You need, in my experience, a proper fixed machine that has been build to be ridden as such. I was bashing quite a biggish gear but I loved it, however, I ended up shipping the chain (for the umpteenth time) and without a lock nut, the chain stuck in the stays forcing my cog off which ended up stripping the threads from my 1970's Campy hub. Live and learn.
In summary, fixed is fab, but ride the correct equipment. A cheapy-cheap cheap bike may be cool, but it will cost you more in sweat when it farks up that it would cost to buy one that was designed for purpose.
