Over the past two years, the PostMark disk performance has improved with each succeeding Ubuntu Linux release that was tested. With the forthcoming Ubuntu 12.10 there's a nice performance gain.
The NAS Parallel Benchmarks have been improving too along the way. None of the NPB tests regressed on the newer Ubuntu releases but had significantly improved for a number of the workloads. Ubuntu 10.10 shipped with the GCC 4.4.5 compiler, Ubuntu 12.04.1 LTS with GCC 4.6, and Ubuntu 12.10 is packing GCC 4.7.1.