I just switched from spd's to speeplay zeros this week. I choose them mainly becuase I liked the idea of double sided entry. They are very easy to get in and out of.

As others have mentioned, the float is adjustable and can be completely eliminated. The float felt very strange coming from spds and I've discovered that I swing my left heal out sometimes and my left foot generally moves around while my right feels solid and stable. I might just lock down the float eventually, but want to try working on my pedel stroke first. It seems like having a bit of float would be a good thing on the knees, but I'm no expert.