Like a lot of people, I use the Speedplay Zero Stainless.
This is my second pair of Speedplays. The first one was the X series in chromoly. The Zero offers a couple of significant improvements over my first pair of Xs. First, the bearings are better. I think they are bigger and there are more of them - I know that there are more of them. The X bearings needed service pretty regularly, fortunately it's ridiculously easy. I've serviced the Zeros and it's just as easy. You take this tube of grease with a pretty standard gun head on it (same as for my mountain bike fork) and you unscrew a little screw on the outside of the pedal, and then you pull the trigger until she goes "click." Actually, you pull the trigger until all the nasty grease it out and clean grease starts coming out by the axle, I just thought people would appreciate a Lebowski reference. That's it, you're done.
Another improvement versus the X stainless is the float adjustment. I have my float window pretty dialed in, and prefer having the ability to set where my float occurs and what the limits are. It's actually pretty sweet. I used to ride Look knockoffs (they were well known, all the old timers will have had a pair) and coped fine with no float, but I like a little bit. It's good. New Speedplay users will definitely feel like they're getting their freak on when they feel all that float.
The stainless axle shows no signs of any rust/tarnish/whatever after two plus years of mostly wanton disregard.
Some people have a problem with cleat durability. They recommend changing the cleats every 5k miles. I am a little behind schedule on that (like 5k miles) but not to worry I just switched one cleat the other night. Maybe the left cleat will get done next year?
One super cool thing about the Zeros is that you can rebuild like almost the whole thing. They sell almost every part that goes into the things, so if you crash and one of the bowtie things gets bent or a plastic thingamaboo cracks, you can just replace it.
Clicking in and out becomes super second nature in no time flat.
I might have more love for these pedals than any other part on my bike. They are reasonably priced, sexy, as pro as you want, they look cool, they work awesome - I don't know, if you have some other pedal feature that I haven't covered there you think about pedals more than I do.
Rain sucks. I wanted to do Greenbelt tonight. Finally producing some okay power in the new position. Did the crisscross threshold interval (go from tempo to threshold in a since wave with 4 minute period for 40 minutes) last night and it went fine. Except it was on the trainer. I'm done with that thing, except that I'm not. F.