For those curious whether Intel's queued up driver changes for landing in the Linux 3.12 kernel offer much in the way of better performance, for at least common Intel HD Graphics systems it doesn't appear that way.
The Intel DRM driver has a fair number of changes that will be found in the upcoming Linux 3.12 kernel. Not many of the changes though are directly performance-related, aside from those Intel Haswell owners sporting Intel Iris Pro graphics where the eLLC cache is finally enabled. This dedicated on-die video memory has the potential of improving the performance a lot but we're waiting on hardware to test; it looks like System76 will soon be sending out a Galago Ultra Pro laptop with Iris graphics for Linux benchmarking at Phoronix.
Anyhow, being curious about the performance of the Intel DRM driver changes that are queued up for Linux 3.12, I ran some drm-next benchmarks this week comparing it to the stable Linux 3.9/3.10/3.11 kernels. Testing was done from a System76 Gazelle Professional laptop with an Intel Core i7 4900MQ Haswell CPU boasting HD Graphics 4600.
Overall, there weren't any major 3D performance changes to find out of the drm-next code for this common Intel Haswell graphics core when compared to recent stable Linux kernels. The benchmark results in full though can be found on OpenBenchmarking.org at 1309040-SO-INTELHASW69.