A big surprise today is that Mesa 10.2-devel is being accepted into the Ubuntu 14.04 archive... It was just last month that Mesa 10.1 was added to Ubuntu 14.04 with its release last month and provides a big update to the open-source 3D graphics driver stack. While Mesa 10.2-devel isn't being officially released for two months, Canonical is pushing the experimental open-source 3D graphics drivers into the Ubuntu LTS release.
The likely reason for pursuing the Mesa 10.2-devel support prematurely is so Ubuntu 14.04 LTS will have Intel Broadwell graphics support. With Mesa 10.2-devel are also performance improvements and other new functionality as already talked about in dozens of Phoronix articles. I'll also write a feature recap so far of Mesa 10.2 Git for those not up to date on their Phoronix reading.
Hitting trusty-proposed was mesa 10.2.0~git20140319-0ubuntu2. Canonical has already revised their out-of-tree Mir patch for this new Mesa version. More Ubuntu 14.04 LTS benchmarks from its updated graphics stack will come shortly.