I use them on the road bike. They are great there, but not so good on a mountain bike in the mud of the east coast US. When I lived in Colorado, they weren't very good there either, where the trails were made of rock and gravel. The little elastomer return spring on the cleat just doesn't allow for quick engagement against the resistance of goop and grit. If the slightest bit of gunk prevents the cleat from sliding all the way forward on the pedal, to allow the spring to pop the ramped clamp over the back of the pedal surface, then the pedal won't hold the cleat. Also, if you are a rider who uses a lot of body 'english' on technical trails, then you'll twist your feet far enough to just glide right out of the pedals.
On the road where they never get very dirty, and where your pedal motion is very consistant and controlled, they are wonderful.
I'd love another set for the commuter!
Your results may vary!
Drowning in Retro!