The only real difference between that and the 6800GS is the fact that it can handle 4 cacluations per pixel line, per clock, while the 6800GS can only handle 2.
That'll b excellent for all games, trust me, and its a great budget card.
Since its cheaper than the 6800GS too, its worth the extra money from the 6800XT you specified, and will perform alot better in new games
The fact they disscontinued stock, just means they aren't producing the other 6000 series cards anymore, so basically retailers are tryin to get rid, but there are alot better deals out there now. I mean, for another $15, you can get a card alot better, that'll handle the newer effects (Like HDR) better.