There's still a number of weeks before KDE SC 4.6 arrives, which will provide some KWin performance optimizations, but Martin & Co largely have their focus now on KDE SC 4.7. Just last week the KWin code for this summer 2011 release hit the milestone of compiling the OpenGL ES code and this week this code is beginning to actually work.
Martin is reporting via his blog that this weekend the first windows are being composited under KWin using OpenGL ES 2.0. There's still some artifacts being displayed and such, but this is great progress. Right now most of his testing is being done atop the Nouveau Gallium3D driver with Mesa's OpenGL ES 1.1/2.0 support.
Martin ends, "It is incredible how clean the ES code looks compared to the glx backend. I’m really looking forward to be able to drop the legacy OpenGL code and I hope to have the ES port in a state that users can use it as a runtime replacement on desktop systems as well. It would be nice to provide users a modern compositing backend."
It will be interesting to see if this new code path for KDE's compositing window manager will now work better with the LLVMpipe driver as a means of providing CPU-based software acceleration by leveraging Gallium3D and the Low-Level Virtual Machine.