The Intel 2.12 driver is their quarterly X.Org driver update and it focuses on delivering bug-fixes, improved overlay and XvMC with GEM support, and major performance improvements. Just last night a Phoronix article was published that shows the major Intel 2D performance improvements with this newest DDX driver compared to the older xf86-video-intel 2.11.0 driver from last quarter and then also the Intel Linux graphics driver stack found in Ubuntu 10.04 LTS.
The release announcement for xf86-video-intel 2.12.0 can be found on the intel-gfx mailing list.
Intel has also released their 2010Q2 package, with that release announcement being found here. What Intel is calling their 2010Q2 package is the xf86-video-intel 2.12.0 driver, Mesa 7.8.2, and libdrm 2.4.21. Intel also recommends using a Linux 2.6.35 kernel (a release candidate for now) for the latest DRM, which allows Intel Ironlake customers to benefit from H.264 VA-API decoding.