Ubuntu 12.10 has a 'low graphics mode' that disables some dash and launcher effects like active blur and transparency. It also darkens dash for improved visibility. By sacrificing these effects, you can improve Unity performance.
This low graphics mode is enabled by default in llvmpipe software mode which is used as a fallback method if your system doesn't support 3D hardware acceleration. However, on high end systems, you can enable low graphics mode without getting into fallback renderer.
Low graphics mode can be enabled by adding following line to ~/.xprofile (if the file doesn't exist, create it)
Logout, and come back for the effect to take place.
To check if you are running llvmpipe software mode or not, run the following command:
In software mode, you will get output like this:
GL_RENDERER = Gallium 0.4 on llvmpipe (LLVM 3.1, 128 bits)
GL_VERSION = 2.1 Mesa 9.1-develGL_VENDOR = VMware, Inc.
Low graphics mode changes are mostly same as disabling blur and transparency effects through compiz config settings manager (CCSM). You can use either of these methods to improve Unity performance on your desktop.