There are a lot of hills around here. Fixies would slow me down. Also there are many potholes-- how do you bunny hop them on a fixie at 30mph? Still I think that both fixies and tallbikes are cool. I'd do a single speed before a fixie or a tall bike as a commuter. I'd also use brakes. I'd be a bit concerned about the effects of long term fixie use on the knees.

I've know a few of the old bmx friends who have blown out their knees before they where 30. To me its not the rpms, but the back pedaling to brake. If you had a level commute that would be less of a concern. Many Pittsburghers are commuting and messengering on fixies.