beane,
i have used speedplay zero and light action. DH and i now have zeroes on all our bikes. i didnt have any problem with the light actions.
1) some people prefer a larger platform, but i dont miss it, i stand a lot when climbing and when leaving stoplights, and i have no problems with the smaller platform
2) i do prefer less float but cant say that it really created a problem.
3) yes, they are a real pain when the cleats are packed with sand or dirt or mud. but the only time you ever have a cleat problem is when walking, never when riding. if they're jammed with mud or sand it's really hard to clip in, and once i had to pull my foot out of my shoe at a stop because the cleat would not budge out of the pedal! but that happened exactly once, and the only other time i had a problem was going thru deep, soft washes at el tour and i had to clean out the cleats before riding on. but you just knock the shoe against the ground to dislodge all the gunk. no biggie. also, as far as the cleats go, they are the hardest to walk in, but buy the covers and they work perfectly.
4) no.
5) yes, a couple times, but no more than any other type pedal - remember lance at the opening time trial he lost to dave z at le tour?
6) dual-sided entry!!!! cant go wrong!!!! ever!!!!