waxman, for me it wasn't the short mounting distance (any more), although it was at one time. Rather, I like having the pivot point of the toe release motion being on the tibial axis. Without a turntable, this isn't possible, and there is therefore radial force applied to the tibia that isn't otherwise applied.
The real issue, as I understand it, was that consumers didn't like the lack of a real positive "click in" experience. That was the discussion for years. And yet it seems that they were pretty popular, especially when they joined forces with Dynastar and Rossi.