I have Speedplays ... one of the X series, I think the Titanium ones. I can't compare them to other cleats since they are the only one's I've ever used, which might be saying something if you're looking for something to learn on. I can't say if they're more difficult to learn on than something else, but I did fine learning with these. I guess they're different from some of the other clips in that you twist your foot out to get out of them, which can be awkward for someone who is used to something else. Yet, you clip in easily by just stepping into them, on either side of the pedal.

My husband switched to these back when he was doing a climb, pulled up hard and his foot came out of the clip. Since you twist your foot outward to get out of these, it is virtually impossible to accidentally unclip with these.

Here's an exerpt from the Speedplay website about the X Series.

The Speedplay X Series' innovative design and unrestricted float changed the shape of clipless pedals and continues to prove that user-friendliness, comfort, and improved performance are all attainable in a simple, lightweight package. The unique shape of X pedals provides knee-saving lateral rotation, without the self-centering action inherent in most pedals - your knees don't have to work against spring tension. The compact, low-profile shape of X pedals positions your foot closer to the spindle for optimal power transmission and unmatched cornering clearance. And their dual-sided design ensures easy entry and exit. X Series Pedals were Speedplay's first double-sided design and earned a prestigious Designers Choice Award from ID Magazine, the premier publication in the field of industrial design.

A friend of ours has the new Shimano clips (don't know what they're called). He likes them, as does the owner of our LBS shop. I don't know anything about them except that you don't twist your leg out to get out.