This is one of the misunderstandings that I want to see resolved between KWin and Mesa/Xorg devs. We need to know what the other side means. E.g. if I say "We need to improve Compositing", I mean improving User Experience and if driver devs read this as "We need to ship more eye candy", we have a problem :-)
In the past with just Compiz it might have been that especially in the beginning there was a large emphasis on eye candy, but this has never been the case with KWin.