Dangit. Says $309 now. Oh, well. I'm also waiting for the 1tb drive from Hitachi. They claimed they would ship to retail in 1st quarter, OEM 2nd. Towards the end of March, two OEMs began advertising 1tb drives and no sign of them in retail yet. 😡
As for the maximum storage capacity, Apple's obviously only going to list the maximum capacity they've tested. Back when I used to build a lot of PCs, most of the motherboards I bought had all kinds of qualifiers listed in their specs. advising that they "...cannot guarantee compatibility with XX meg memory modules as there were no XX meg modules available for testing at the time of printing. A BIOS update may be necessary..." Same with hard drives when manufacturers started integrating controllers into the motherboard. It was always, "It'll probably work, might need an update, but no guarantees for hardware that didn't exist at the time the product was released."