Among the fixes that landed in the latest xf86-video-intel 3.0 snapshot include fixed video output using sprites, more restrictive tile constaints for i915g devices, prevent discarding active upload buffers, Ironlake pipe-control is now a full pipeline flush, out-of-bounds access fixes, and various other acceleration changes. There's also build fixes for the latest X.Org Server 1.15 pre-release.
In the past week, Wilson has made 52 changes to the driver and details can be found via the release announcement. The major feature of the Intel X.Org 3.0 driver is the SNA acceleration architecture by default over UXA, which means faster 2D performance for nearly all Intel hardware.
At first there was also XMir support for the xf86-video-intel 3.0 driver, but Intel decided to drop that support. From Chris Wilson's comments today in the mailing list announcement, "There is one more feature planned to be completed for 3.0", he didn't specify what the last feature it will be. It might just be some subtle work on an SNA 2D feature or maybe it will be something more interesting like the landing of Intel Broadwell support -- Haswell's successor in 2014.