If you have a 7800 and move to a G80 which no doubt many will do it seems like a large amount of wasted money to me. In your case being only around $30 go for it and jump on the offer.
I stepped up from the 6600GT to the 6800GT. They got the card back to me within a little over a week I believe.
The thing that sucks though is the prices on their website are ridiculously high compared to a place like newegg. The 6800GT was still listed as $399 when newegg had it for like $325 so that's a drawback of their step up plan.
I went and bought the 7900gt today......up from the 6800xt....so I guess I'll be a little higher on 3DMark05 now at 4060? It is my opinion that this card, at $320, shipped will be more than adequte for awhile!!! Doh!!!!!!!