My experience with Speedplay has been quite opposite to IAmSam's.

I find them fairly easy to clip into and very easy to release from. That is, not so easy they're dangerous--they hold on 100% until I'm ready to get out, then they quickly let me go.

I've only tried one other clipless system. I had some Shimano SPDs in the late 90s and liked them. I like Speedplay Zero even more.

The Zero models are so named because they have an adjustable range of zero-resistance float. You can dial in how far you want your heel to float in and out. Once it reaches that limit, it will stop, and at that point a deliberate, moderate force makes it release. The actual release force is not adjustable.

The only downside to their system is the large "cleat," which is actually the locking mechanism, on the shoe. It makes walking pretty awkward. I've been using coffee shop covers that snap on over the cleats to protect them and give more traction, but these are a nuisance to carry and to put on and off. I just recently changed to their walkable cleats, which are the same as their other models but with the addition of a plastic fairing surrounding the metal parts.