I'm gonna bet that they ship at a 300MHz core. Just my speculation. All the more reason they wanted nobody to display hard benches with the sample cards clocked at 325MHz they gave to some sites. They probably didn't want to raise everyones expectations and then shock everyone by dropping it to lower core speeds at the last minute.
Not to mention the fact that the drivers are of course immature as early as they are. If ATI can ship the card at say, 325/325 with great initial driver support, the 9700 is gonna own Nvidia big time, at least till their "big gun" comes out!