According to HardOCP's review of the MSI Lightning Xtreme 3GB GTX 580, yes, but only in certain games and settings.
Here in FEAR 3 they were able to enable 4X MSAA on 3GB GTX 580s with playable framerates while the vanilla GTX 580s only could do FXAA (a shader based AA method) at 2560x1600.
In Metro 2033 when they turned on 4X MSAA and Advanced DoF they were able to hit the VRAM limit on the vanilla 580, but the 3GB GTX 580 ran it at playable framerates.
However, with all the other games they tested, they were hard pressed to hit the VRAM limit on 1.5GB GTX 580s and also maintain playable framerates on the 3GB GTX 580s with the same settings at 2560x1600. So in most cases, 3GB is still useful only for multi-monitor gaming. Perhaps with some upcoming games like BF3 the 1.5GB limit will become more pronounced, but currently its only a handful of games that will have issues with a single monitor at 2560x1600 and high AA with only 1.5GB VRAM.