I hear the end of April, but ATI is having the same problems as NVidia did with the faster memory and .13 shrink die size.
Expect the fan to be much louder with a DDR2 setup.
Until they find a way to cool these chips properly without the noise, it may be a later release. I'm also waiting for this card as I want to get my moneys worth paying that much for a graphics card.
The 256meg version will be going for $499.00 but in reality around $479.00
It also depends upon how well Nvidias R35 does as they will be releasing a 256meg card also.
It will be a battle for price vs performance.