My computer has an Nvidia card, supported in Trisquel. It has 1GoB memory.
It really does not give brilliant performance in games. I barely get 30FPS in
SuperTuxKart. So I think it is mostly hit and miss. Nouveau gives 3D
acceleration in things like GNOME which is all I use it for.
However, patches have been submitted for Linux kernel 4.7. They significantly
increase performance, apparently: http://www.phoronix.com/vr.php?view=23064
So don't lose hope yet. I will try them out with Super Tux Mart sometime.