Nouveau vs. NVIDIA Linux vs. NVIDIA Windows 8.1
To no surprise given the GTX 460 and GTX 680 have no form of re-clocking right now in Nouveau while the re-clocking support for the aging GeForce 9800GT was unstable, the NVIDIA binary driver on both Windows and Linux is many times faster. The NVIDIA Windows vs. Linux results were part of the recent 13-way comparison of the two operating systems.
The results will be much more interesting when proper Nouveau re-clocking is finally here.