I am running a 18.104.22.168 kernel using Nouveau on an nvidia pci-express card. Seems to me games like penguin racer and such should run fine on this (even if not as well as with the proprietary nvidia drivers). They run, however, as if there were no direct rendering at all. Even chromium which ran fine on my old system using a junk Matrox card bugs down here. Nouveau's bootup sequence says DRI active. Man page list three options for the driver and I let them all default.