Most of the roadies I know and ride with use SLs or Keos. Some of the faster riders I know are on speedplays - even worse to walk on - you are sacrificing a lot for 'performance'.
IMO, really there are only very 'marginal gains' to be had with these - so 'proper'- i.e. Cat 4 and up - racers might go that way.
For most of us 'club' and sportive riders there's no reason I've seen to leave SPDs apart from peer pressure.
Also, I REALLY prefer to be able to walk around before during and after a ride without looking like a duck.
The weight issue can be dealt with as there are light / stiff shoes and SPDs.
My personal wish list is for these:
http://www.rutlandcycling.com/31497/Ritchey-Pro-Road-V4-Micro---Clipless-Pedals.html
- amazingly light road specific SPD pedals, and a pair of these:
http://www.chainreactioncycles.com/Models.aspx?ModelID=69969 or the new Mavics.
If I get em I'll report.