I had (still have it, actually) a White Industries ENO hub on my SS mountain bike for three years, before I built up a true SS this year. It is smooth as butter after 3 years of use. I know they aren't extremely light, but they are pretty bulletproof and reasonably priced. If you don't care about money or weight, get a set of Phil's - I just built a set up for my fixed gear, and they are some incredible-looking hubs. The bearings are smoother than anything I have experienced, as well. And from what I hear, they're the last hubs I'll ever buy for this bike.