In an earlier article benchmarking multiple Linux file-systems on Linux 3.12, there were some disk/file-system improvements to find. Now with testing as of the latest 3.12 Git kernel yesterday on a completely separate system, I'm still seeing positive disk numbers.
Over on OpenBenchmarking.org I uploaded 1310227-SO-LINUX312I00 for benchmarks between Linux 3.11 and 3.12 Git on a Core i7 3960X "Sandy Bridge" Extreme Edition system with a 64GB OCZ Vertex SSD with an EXT4 file-system, 8GB of RAM, and an AMD Radeon HD 4850 graphics. The HD 4850 graphics on the open-source Mesa Gallium3D driver wasn't any faster for the i7-3960X EE system, but the disk results were what was interesting.
Embedded below are some of the disk results while click the aforelinked result file for details and benchmark data in full. There's also the Core i3 Haswell and Core i7 Haswell benchmarks from Linux 3.12 too. Linux 3.12 brings with it many new features.