Nouveau Linux 4.8 + Mesa 12.1-dev vs. NVIDIA OpenGL Performance
Running Nouveau out-of-the-box on modern NVIDIA graphics cards is basically an unplayable experience... Since with any recent NVIDIA GPU the boot clock frequencies are very low and Nouveau doesn't yet have any dynamic re-clocking support and thus any re-clocking must be done manually. As shown in these Counter-Strike: Global Offensive results at 1080p, manually re-clocking to the 0f performance state is enough for the GTX 680 and GTX 780 Ti to deliver 60+ FPS but still it's a ways behind the NVIDIA binary results. It's a pity the Nouveau boost patches didn't end up being merged for Linux 4.9 for being able to make the open-source NVIDIA results even faster.
The GTX 680 does much better currently with Nouveau than the GTX 780 Ti. It's also a pity about the firmware and re-clocking state for the GTX 900 series.
Again, tests were done with Linux 4.8 + Mesa 12.1-dev for Nouveau.