Nouveau Graphics On Linux 3.15
To not much surprise, there doesn't seem to be any performance differences in moving from Linux 3.14 to Linux 3.15... The big issue remains of the Nouveau driver not yet supporting re-clocking out-of-the-box to allow the NVIDIA GPUs to re-clock to their highest performance / frequency state. Right now most graphics cards run with crippling speeds compared to the binary NVIDIA Linux graphics driver.
There really isn't much to see from these results and the performance is rather crippling until the re-clocking situation is improved, but it's not clear when that work will be ready.