AMD driver support isn't that bad, they release new revisions all the time, so does Nvidia. Driver support isn't a valid argument considering both manufacturers are on the ball with driver releases.
If the OP is concerned with SLI however, than I can understand why he would lean towards the GTX560ti, 2 of those oc'd to 1000 core would be more than adequate for a couple years at least.
Nvidia seems to fix the issues alot quicker. That, and the scaling on SLI/Crossfire seems to be better with nvidia (except 6000).
Get a 6950 if you really want to, it's a fantastic card.