Nouveau Open-Source NVIDIA Tests On Linux 4.8, Mesa 12.1-dev
The GTX 680 and GTX 780 Ti could run BioShock Infinite fine, but their performance leaves a lot to be desired... This was with the GTX 680 and GTX 780 Ti manually re-clocked to their highest performance state currently available through Nouveau DRM on Linux 4.8.
When running Counter-Strike: Global Offensive at least the GTX 680 and GTX 780 Ti deliver playable frame-rates at 1080p. Do note that due to the current state of the Nouveau DRM driver with re-clocking, etc, the GTX 680 is indeed faster than the GTX 780 Ti on the open-source driver. The GTX 980 Ti is the slowest card tested on Nouveau in this article due to its lack of re-clocking.
Nouveau isn't good for 4K gaming at all until re-clocking is fully addressed.