I just started riding fixed two weeks ago, a Trek 330 conversion at 44/15 gearing. Not too many hills around here but when I do have to climb one I find a fixed gear to be easier going up (probably due to the lack of coasting, the low pedal carries itself back around to the top due to the wheel's rotation, making for an easier climb); going the way down can be a little scary at first. I guess you can either go at it and pedal hard down, or try to just let the bike do its thing by "ghosting" your legs on the pedals, just letting the pedals do all the work. I wouldn't recommend that though, it's probably better to be in control of how fast you're going. I usually use a bit of resistance to keep my downhill speed low, so that I don't have to pull hard to stop at a red light or stop sign, etc. It's a great workout, though.