Among other fixes, Unity 6.8 sets out to address some of the performance problems of this default Ubuntu desktop environment.
There's been no shortage of Phoronix articles for the Ubuntu 12.10 cycle looking at how the Unity desktop is so slow compared to other desktop environments, in part due to problems with Compiz. While some improvements have been made, there's also been more regressions.
Developers hope Unity 6.8 will improve things a bit by taking care of some visual and performance problems. One of the main performance fixes is trying to improve the performance of the Unity desktop when using the Gallium3D LLVMpipe driver as the fallback method for software accelerated when no supported GPU/driver is detected. However, Unity on LLVMpipe may still be too weak for the ARM desktop.
A full list of Unity 6.8 changes can be found here. Of course, you can expect Phoronix benchmarks in the coming days to see how the OpenGL and 2D performance now is with this updated Ubuntu desktop set to premiere later this month in Ubuntu 12.10.