But the SLI tends to do very very well at higher resolution with AA and AF.
That's the whole point of SLI, you don't buy a board with those capabilities to put it on medium resolution with no AA. It's a power hungry situation that thrives on you trying to max it out, that's where you see the biggest performance gain, not at lowest resolution with no AA and no AF, then you might as well only have one card.
As with everything that's just coming out, it simply needs time to be properly 'adjusted' I guess you could say to the computing scene. All things aren't perfect when first released.