I don't get your problem with the people suing. They were promised X for Y dollars. They only got a fraction of X.
They were promised 4GB. They got 4GB. Complaining that 0.5GB of that runs slow is like complaining that 2GB of the 6GB in my laptop runs at half the speed of the other 4GB.
The only valid complaint they have is that Nvidia said it had 64 ROPs when it only has 56. That's not really something worth a lawsuit, when, as I understand it, the chip isn't capable of generating pixels fast enough to make use of 64.
As I said above, the only people who will really benefit from this are lawyers.