Re: should I?
Are you referring to the Step-Up deal? Yes, do it. You only have like 3 months after purchase date of your 7800GT to use it. I'm going to wait until close to the end of February for my voucher to take place. Hopefully, some new stuff will come out by then. I'll be glad to pay the difference.
*Fact: Microsoft Window's Blue Screen of Death vs Computerforums.org's White Screen of Death. Which is worse?