The 9800XT simply isn't worth the money. It's not a revolutionary card, in fact it's not even a evolutionary one.
The onboard thermal diode has been around for a while, of course not on video cards, and frankly doesn't really bring any truely useful function to the scene.
If you overclock your card and you get artifacts, guess what, it's clocked to high.
For small 5% increase in overall speed ATi is doing nothing more than taking advantage of those less educated about what thier getting at a premium price.
This is very similar to the situation between the 9800 and the 9800 Pro, except of course in reverse.
I have a 9800 Pro myself and I do like the card, however my card does XT speeds already.
It would be better to wait until Spring before rushing out and paying to much now.
You know for the extra that you pay for the XT you could go out and get a decent watercooling system. <<<< A much better idea all the way around