I like the Look Keo's - the only things I don't like about them is the cleats are slippery to walk on and they wear out quickly. Mine did come with cleat covers, but they're a pain to fiddle with so I don't use 'em.
I've been wanting to try Speedplays. I hear the dirt issue in the cleats is a pain but I like the two sided design. I think that would be a huge advantage.