I went to the above bike shop today and test rode a Surly Steamroller. It was great! I'll definitely want a flip-flop hub though. The fixed gear thing will take some practice.

One question: the guy at the shop said I need a whole new rear wheel to convert an old bike to a single speed. Is this true? I'm assuming hubs can olny be switched out if the wheel is re-laced? He said putting spacers on a hub meant for a multispeed bike would be too dangerous...