I just updated to the latest nvidia driver: System settings -> software sources -> additional drivers tab.
Looks like they have fixed the screen blanking issue, I just watched a whole movie without having to move the mouse to show the screen again.
The new one is supposed to vastly increase performance too:
New NVIDIA Driver ‘Doubles Performance’ on Linux | OMG! Ubuntu!
Nah... sad to say I was mistaken. the new driver has not fixed the screen blanking issue.
I tried turning off the energy star features with "xset -dpms", but this has had noeffect either.
Oh well... I guess we'll have to decide between better performance and moving the mouse every fe wminutes.