I've been riding a fixed gear for 12 years now, and I like it better than my geared bike. The fixed is just as fast for most trips because you have no choice but to push the gear no matter what. On the geared bike I tend to leave it in the low gears too much, unless I'm riding with a group.
The only time I don't like the fixed gear is for long downhills, when the pedals tend to get ahead of me.
OTOH riding the wrong gear into the wind for long flats doesn't sound like much fun either, but it's not very flat around here.

em