for a 24" screen at a normal viewing distance, this doesn't add much
I think it could add quite a bit of wow-factor also on a game like a platformer.
It would make the scene have actual depth in a much more realistic way then you get with just a 3D screen.
Hard to explain properly, this old demo I was involved with shows the effect somewhat:
Not as good as it could be though
I think it would also work pretty nicely in a 3rd person game.
Not adding much gameplay, just more immersion, and something you could add if eye tracking and head tracking was common...
Ah, now I understand what you are on about. 3D without the glasses, like in the Firephone, right? now THAT is actually cool, even though still just a part to the full 3D expierience (no real 3D effect, same image to both eyes). But it is more headtracking than eye tracking if my memory serves me right.
Still, question is if it adds enough given its price for hardware and software integration, especially in a time and age where you can have the full expierience by going VR (or at least you could if the VR Goggles would already be here, a PC to drive them would be affordable and the software would be written... so if today would be some day in about 3-4 years 
).
