After a few years of comparison testing over my weekly exercise route and on longer 30-60 mile rides I have concluded that (for me) I get no recognizable benefit from being attached to the pedals. I've tried power grips, old school slotted cleats and toeclips with straps, and finally SPD clip in shoes. Except for certain bike styles ( high bottom bracket recumbents and fixed gear riders) or actual racing, I think any retention pedal system to be a solution to a non-existent problem. I think many riders are fooling themselves into believing that a retention system gives them significant performance gains. I'll bet many riders have not tried a plain BMX style pedal on their good bike and so have nothing to compare with. I've tried them all and my evidence shows no significant gains. Perhaps my spin is efficient enough. I am not racing for money. If I were, I might want to be on an even playing field equipment wise since I wouldn't want my feet slipping off in a mad sprint, causing others to crash. I rarely if ever ride in a pack so its not a concern to me.