The C-Ray performance is currently leveled out with GCC 4.6.
An earlier performance drop in 7-Zip compression has been addressed in Ubuntu 12.04.
The video encoding performance with x264 and libvpx appears unchanged, at least for the lone test system used in this initial testing.
Stay tuned for more Ubuntu 12.04 benchmarks in the coming weeks. So far from the performance aspect Ubuntu 12.04 "Precise Pangolin" is looking positive. As well, the Ubuntu 12.04 ARM state is looking extremely positive.