Making the RC6 engine for Intel graphics the default was reverted at the last minute due to instability, http://www.phoronix.com/scan.php?page=news_item&px=MTAzN.... It can still be enabled manually by adding i915.i916_enable_rc6=1 to the kernel boot parameters, just like 3.1.

Another interesting change concerning Logitech Unifying devices is that multiple devices are now given separate /dev entries, instead of being multiplexed into one device.