Speaking as a current Nvidia user who also have 2x 6950s unlocked, AMD/ATI drivers for the 6900 series is pretty good RIGHT NOW with the 11.1 series leaked drivers, which is practically the same as the 11.1 WHQL drivers being released in less than 24 hours. Most games - OpenGL, DX9, DX10 and DX11 that I've tested ran amazing fast, beautiful with graphics maxed settings ingame and ccc (control panel) and most importantly stable.

I was one of many unlucky 400 series owners whose card had crapped out in less than 3 months use (purchased in June 2010). Fixed now via RMA - bad memory module or related to it, but this drove me to pickup the 6900 series instead of going to the 500 series.

I would still say Nvidia has the upper hand in driver / feature support but AMD is getting much closer. There are still some game or game engine bugs they need to work on but at least they are working on it.

But when the 6990 card comes out, I'm sure AMD will offer a faster or more optimized driver for it to show its potential. Just like how the 500 series came out and had even more optimizations vs the initial 400 series drivers from the green team.

It is usually more stable to get the refresh than version 1.0 of a new architecture.