Maarten Lankhorst has issued an immediate call for testing of Mesa 10.1 so that it can be pushed into Ubuntu 14.04 ahead of its feature freeze, which is coming up in just two days on 20 February. At the moment in Ubuntu 14.04 is a Mesa 10.0 point release.
Mesa 10.1 brings many new OpenGL features, new hardware support, and as with most Mesa updates is a very worthwhile upgrade for users of the open-source Linux graphics stack. There's been many articles about Mesa 10.1 on Phoronix while there's also the Mesa 10.1 feature overview. Mesa 10.1 itself is in a release candidate stage but should be officially released later this month on 28 February.
Those wishing to test out the latest X.Org/Mesa packages on Ubuntu can use the xorg-edgers PPA. Another way to get the latest open-source user-space graphics driver packages even on stable Ubuntu Linux releases is using the highly popular Oibaf PPA.