What game? I hit 2gb on one 1080p display with BF3. And I notice an occasional FPS drop because of it. Also with a few other games that hit over 2gb: Crysis 1, Crysis 2, Minecraft, Skyrim, and CivV. All of these games are staved because my 680 lacks the amount of vRAM and that is with one 1080p screen.
Clearly the card is meant to do more than what the 680 can do because of its 2 cores but it cant do much more than the 680 because of its 2gb or RAM.
I also I know for a fact AND from experience. I own a 6990 not as powerful as the 690 but still has 4gb of vram (2gb usable) and it is more that powerful enough to handle BF3 on ONE 1080p display. But guess what? Once I hit 2gb my steady 60 FPS stays at the low 50 to mid 40s.
I am not going to pay $1000 for a card that will run out of vRAM before running out of GPU juice.