In addition to finding several positive comments on the Powergrips option, I should add that in reading dozens of threads on clipless pedals, that the most consistently positive responses were in regards to the Crank Brothers egg-beaters design. Nearly everyone who compared them to the Shimano clipless pedals liked the egg-beaters better. With many of them liking the mini-platform "Candy" design.

http://www.crankbrothers.com/eggbeater.php

http://www.crankbrothers.com/candy.php

Can't say myself, as I've never used any of them. Only reporting what I found from reading several hundred posts.