The acquisition of ATI made things and people a little bit insecure and out of focus, so the chip won't be read for December as originally planed.
We are sure that R600 team has got some problems as well but it looks like they can handle it but with a delay of course.
It looks like Nvidia's G80 will be out before but R600 still looks more attractive. This is what our own Charlie Demerjian reported he other day, here. Nvidia might have up to three months lead with its new high end product and this is a lot.
Until then, ATI has to hold the market attention with sub $ / 399, R580+ Radeon X1950 XTX card. It doesn't sounds good for ATI in high end market. µ