If nothing else, the fact that I can't shift makes it much easier to just deal with the fact that I have a hill coming up, and I have to get the hell up there somehow, so you just pound it out on a fixed gear. I also think it's a lot more fun to climb on a fixed gear rather than a road bike, up to a certain point (that point is embodied by 18th St. here in PGH; anything steeper or longer than that and I am no longer enjoying my fixed gear riding experience). So basically what I'm getting at is maybe everybody in this thread is right. dutret is right because there is little to no real mechanical advantage to fixed gear riding up hills, but rather a series of psychological advantages that make it seem easier, coupled with the fact that I know when I'm starting a hill on my fixed gears, I bomb it at the bottom so the momentum can carry me part way up the hill. Another thing with fixed gear that could maybe make it feel easier is that if you're staying enough in front of the pedals and not relying on them to throw you over the dead spot at the top, or pull you through the dead spot at the bottom, it makes it easier to turn nice little circles without jerking or wasted effort.
So, whatever, I like bikes.