The foundation of R700, the chip called RV770, is taped out and it looks very promising. Just as ATI based many products on RV670, it plans to use the same tactics for the RV770.
This chip will be used for mainstream, performance and high-end products and we can tell you that it should end up significantly faster than RV670. From what we have learned, it should be more than fifty percent faster, although we have heard even higher numbers.
The RV770 is DirectX 10.1 compatible and it is made at 55 nanometers by (who else?) TSMC. This baby is scheduled for late Q2, if not early Q3.