Interestingly, Steve/Hardware Unboxed posted an updated review, taking into account the OCs. He does a good job of comparing stock 7800 XT to stock 7900 GRE, OC edition 7800 XT to OC edition 7900 GRE and stock 7800 XT to OCed 7900 GRE.
HW Unboxed 7900GRE review update
Basically, the OCed 7900 GREs are about 8% more powerful than the OCed 7800 XTs for that 10% extra cost. (And about 13% faster than the stock 7800 XT.) But factor in the fact that the OCed models of 7800 XT are generally more expensive than the MSRP for stock and the fact that at least a few models of OCed 7900 GREs are currently priced at the $550 MSRP, and the discrepancy between pricing and performance becomes basically zero, and the 7900 GRE becomes even more compelling, especially for people upgrading from previous GPU generations.
But the most interesting development in all of this is that all of the hubbub and dissatisfaction from much of the fanbase has forced AMD to announce that the strict limitations on overclocking that they obviously deliberately imposed on the 7900 GREs to avoid cannibalizing sales of the 7900 XT were actually a "bug" that will be fixed soon. So, we'll probably likely see those already decent OC performance numbers going up quite a bit with the next Adrenaline update.
So, in just a couple of days the enthusiast fanbase has managed to pressure both one of the largest YouTube hardware DUI enthusiast channels and the second largest computer parts manufacturer to change courses on some questionable decisions. Not a bad week for the community!