I've been riding Speedplay Zero pedals on my steel steed for about six months now, and I just got the Ti version of the same pedals for my new Madone. They are outstanding pedals... functionally, I can't think of anything bad to say about them.

However: Take to heard what other posters have said about keeping them clean and lubricated. I was negligent about that at first, and I did an embarrassing tree-falling-in-the-forest move as a result. But if you keep 'em clean and give 'em a spritz of dry lube every ride or two, they're as good as pedals can be.