A couple of things I thought I would chime in on...
Did you notice the increased frequency as of late with official NVIDIA drivers? I think that NVIDIA has finally taken the hint from OEMs/Reviewers/customers and are starting to take official driver releases a lot more seriously. In the past month there has been the official WHQL 71.84, and just last week we see the WHQL candidate 71.89. Not a huge jump by any means, but no less than what ATI typically does month to month with their Catalyst drivers. I certainly hope that NVIDIA will continue this, and that this wasn't a one-off type of instance.
Image quality... ack. Yes, ATI's AA at the official levels are nicer than NVIDIA's, but the difference is not as glaring as it once was. The 6x00's AA at 4X was improved by doing the rotated grid thing, and while it is not "gamma corrected" I would say that the quality differences are not that huge. 8XS looks very nice to me, and I can use that in quite a few games (Quake 3, Call of Duty, Morrowind, etc.). Yes, it cannot be run in games like HL2 or Doom 3 due to the massive performance hit, but for many older games it works just fine.
16X... I am testing a 6800 GT SLI setup, and I can attest that 16X works fine in many games. Running Morrowind at 1024x768 with 16X AA is a buttery smooth experience, and the visuals are stunning. Better than anything I have ever seen before (including ATI's 6X AA). 16 stinkin samples per pixel is very impressive. Again, it doesn't work very well in many of the latest titles, but it sure makes the older stuff look great!
NVIDIA's cash cow right now is the 6600 and 6200 series. Those products are selling like hot cakes, and in each instance they are outperforming the ATI part at that price point. Sure, the X800 will outperform a 6600 GT, but it isn't exactly at the same price point (usually $50 US more expensive). Also, ATI hasn't refreshed their AGP midrange lineup, and so far we haven't really seen any X700's being paired with Rialto. This is an area where NVIDIA is cleaning house. The 6600 GT AGP is the upgrader's card of choice at the moment. A lot of people view the 9800 series as "old" and the 6600's are nice, shiny, and new.
NVIDIA hasn't made many mistakes in the past year, and I get the impression that ATI got a little complacent. Yes, they were the leader into the PCI-E market, but with the 6200/6600 series that lead is taking a big hit. I certainly don't think ATI will sit around for long, and they could have some really impressive leads over NVIDIA if they transition to 90 nm in an effective way. I guess we shall see.
I do love the competition though!