Fixed gear bikes do better on certain hills because the rider doesn't want to drop below the most efficient cadence, and, if the rider does the hill a lot, he will do it in a higher gear (his only gear) than will a geared bike rider.

Now, make that a very long hill that the fixed gear rider hasn't ridden before, and it might just give the advantage back to the geared bike rider.

On the flats and downhill, the geared bike riders just blow past me.