The Linux 2.6.34-rc3 kernel has various regression fixes and other bugs. There isn't anything too prominent besides an EXT3 on SELinux issue that is rather big, but Linus encourages everyone to test out this new release that should be more settled down for the Linux 2.6.34 cycle.
The Linux 2.6.34-rc3 kernel release announcement can be read at LKML.org. We continue to monitor the latest Linux kernel code performance on a daily basis at kernel-tracker.phoromatic.com. While mentioning that, we also monitor the very latest Ubuntu packages and their performance on a daily basis too.