I just did my 1st commute on a fixed gear (I had a Specialized Dolce, got hit by an SUV, totalled the bike, had to buy a new one, went fixed--Giant Browery) and it was **amazing**. My time was cut by a 1/3 because I was spinning a much lower ratio than on my road bike, and I didn't feel nearly as exhausted as I normally do. Maybe this is just because I'm on a high with a new bike and all, but darn, it was awesome.

The one wierd/hard part was spinning down the huge hills by my office and not being able to coast and using only a front break. But I'll get used to that.