I'm not sure I'm gonna be much help
I use Shimano SPD's with Specialized MTB shoes for the commuter bike and Specialized Road Shoes for the road bike. I looked at the Speedplay but I don't have any problems with my knees and several ppl I talked to at my LBS said then don't use them as they could screw my knees up. One guys wife had Speedplays and she couldn't Wait to get them off....said the float was too disconcerting for her. So I stayed with the Shimano SPDs for the road bike I'm rebuilding (he'll be ready Thurs or Fri!
) I wear the MTB on the commuter coz I have to do quite a bit of walking and they were by far the easiest and most comfortable. I went with road shoes for the road bike coz I'm not planning on being out of the saddle cept for climbs, sprints, and to take him out and put him back!
(only on sunny days of course!)
Life should NOT be a journey to the grave with the intention of arriving safely in an attractive and well preserved body, but rather to skid in sideways, champagne in one hand, strawberries in the other, body thoroughly used up, totally worn out and screaming: "Yeah Baby! What a Ride!"