I am really not into the whole fixie scene, but they are actually very very nice to ride, they make hills easier (because the wheel is already turning you don't have to put as much effort in) and you generally have to concentrate slightly harder which is fun (in the same way riding brakeless is fun). Plus its nice not having any cables, mech, brakes to make noises or clutter up the bars.
I managed to build the bike for around £140, bargain if you ask me!