Front brake only on a fixed-gear bike Is it considered safe-enough to only have a front-brake on a fixie in a urban area that has many hills?  I've been considering buying one, but I want to get some opinions before I move forward.
Yes. The front brake provides basically all of the stopping power in a bicycle, and recent tests in Bicycle Quarterly show that, in emergency stops, the distraction of attempting to use the rear brake may even increase stopping distance. Maximum bicycle braking power is achieved just before the bicycle starts to pitch over, as the rear wheel lifts off the ground. Once that occurs, it's trivial to lock the rear wheel with a brake or by using your legs on a fixed gear.

The main disadvantage of having a front brake only in extremely hilly situations is not being able to dissipate some of the thermal load of braking between both rims, so you risk overheating the front.