Fixed for the KDE SC 4.7.2 point release in one month is a bug in KWin's effect chain that was taking much longer than expected, but greater performance will come out of KDE SC 4.8 by fully addressing an issue in the effects chain with only calling the active effects. From there, Martin made other optimizations in the effect chain. With the effect chain being more optimized, Martin is beginning to look at how to optimize KWin's paint paths so they can achieve 60+ FPS rendering on the KDE desktop.
Martin is also looking at moving the compositor into its own thread so that heavy operations in window management and decorations don't slow down the repainting of the compositor. Texture loading might also be looked at as one of the first steps into moving the process into its own thread.
"Overall very nice improvements, I'm happy with, but not yet satisfied as we do not yet reach the constant 60 frames/second." Read more on Martin's blog.