I started riding single speed because riding a BMX was starting to get a little painful for my 35 year-old legs and back, but flipped my back wheel to the fixed side one day 'just to try it out'. I've since removed the freewheel from my hub completely and swear I'm never going back.
Fixed gear certainly does rule.

Use a front brake. Please. I don't need mine very often but have had some instances where I've been pretty damn happy to have it.