The xf86-video-intel 2.99.903 that was released on Saturday has a lot of stabilization work but still isn't yet ready to be called xf86-video-intel 3.0.0. There's many changes ranging from build fixes to hardware enablement adjustments and performance tuning. Some items in particular including fixing V-Sync for Haswell, disabling Y-tiling for Gen4 hardware, DPMS fixes, and handling out-of-memory conditions more gracefully.
The earlier plans for the xf86-video-intel 3.0 driver called for SNA acceleration by default and supporting XMir. SNA is still enabled by default in this release but Intel management decided to not support XMir, the X11 transition layer for Canonical's Mir Display Server in Ubuntu.
More details on the xf86-video-intel 2.99.903 release can be found via the release announcement.