"I've never ridden fixed, so pay no attention to me. But...
If the pedal feels different at the top of the stroke, doesn't that imply that you're not applying power through that part of the stroke? If you were, logically there would be no difference in feel. Only if you're letting the bike drag your feet through that part of the stroke should there be any difference."

-I would say yes. My Commuter (non-fixed) bike is the first clipless pedals I have had other than first generation looks. All my other bikes have been strapped. I do not know if I have developed some bad pedaling habits or if I have too much play in these new-fangled Shimano clip things, but I've got some bad circling at the top of the stroke when I switch back to it after riding fixed for a while (with straps). I'm going to rachet the springs down until I nearly strip the allen screws and see if that helps. If not, back to straps I go.