Phoronix tests Intel's Sandy Bridge in Linux under Mesa 8.0, you can check out the results over here.
"Now that the Nouveau, Radeon, and LLVMpipe graphics drivers
have been tested under Mesa 8.0, what is left? The Intel DRI driver, of
course! The open-source Sandy Bridge Linux graphics support is shining
with Mesa 8.0 thanks to OpenGL 3.0 support and measurable performance
improvements. Intel Ivy Bridge is also ready to run under Linux."