I love my Speedplay Frogs. I have them on two bikes (neither of which are mountain bikes). I've read a lot of internet horror stories about pedals like the Crank Brothers Eggbeaters breaking, and I'm totally paranoid about springs messing up and releasing. With my Frogs, I don't worry about it. Lots of float, and easy to get out of, without having to worry about spring tension and whatnot (granted, I've never used a different type of clipless pedal).

Sorry, I know you said you don't want to pay for 'em.