The Sunday open-source Intel driver release corrects regressions concerning preserving KMS configurations and external Haswell connectors, couple fixes for long-standing issues, and other bug-fixes. One of the bug-fixes goes back to address incorrect rendering on the very old Intel "Gen2" graphics hardware. There's also a Gen4 improvement in the mix.
Chris Wilson made 49 changes to the open-source Intel driver for this release, most of which centered around his SNA acceleration architecture. More details can be found via the mailing list announcement.