I am not going to start an IQ arguement. But I have to say that what he is experiencing is normal. The "jaggies" are more noticable on the nVidia cards when in motion if using anyhting less than 4xAA. They are not bigger or worse. Just more noticable. They roll or crawl more noticably in 2xAA or 0xAA modes. Like chainsaw teeth in slow motion. I have never been able to show this with screenies because when still they look the same. Like he pointed out, it's not in all games either. Just some.
After a long time on a Gforce 4 ti4600, I had a 9700 Pro which ATI replaced with a 9800 Pro in an RMA situation. A few years later I had an X800XL for a few months. I came back to nVidia getting a 7800GT. Very fast and I love it.
However. The first few weeks it took me a while to adjust to using the card. The crawling or moving jaggies were distracting. I was not looking for them and assumed that IQ was identical this many generations of cards later. I'd say they are just different now.
With ATI I often played games without AA in favor of going to a higher res. It looked fine. I prefered it. But with the 7800GT, anything less than 4xAA and the crawlies were there in some of my games. Farcry I saw em all the time. COD2 never.
Luckily I just run my 7800GT in 4xAA mode. So it's virtually unnoticable. Some of the games I need to go to 1024x768 with 4xAA to have fast framerates. But that's ok. Looks wonderfull anyway.
I do have a PC next to this one with an X800GTO2 in it that we use in the house. So I can see games side by side. But that's just it. They need to be side by side and watched to see the difference.
I think a long time ATI user is the only user that can see it. Which makes sence. A few years of training your eyes to one product game after game. You are bound to see the differences when you switch.
Aside from that, I ahve been VERY happy with this 7800GT. But if the X1800XL was not so noisy and about $35 cheaper I woulda switched to it.