RV740 is ATI's new mainstream card, and from what we know, it is scheduled for the second half of 2008. The new card is planned as ATI's ultimate mainstream, and this is what ATI needs to compete with the soon-to-be-launched G94 based 9600GT.
The new RV740 also brings a 256-bit memory interface and it is a 55 nanometer-based chip made my TSMC. The 256-bit memory will move this mainstream card to the next level and will certainly mean that you will be able to set higher settings such as FSAA and Aniso.
We also know that it will be drastically faster than RV630 and RV635, but we wouldn’t expect anything less than that. Currently it looks like Nvidia will have a massive lead with its 9600GT, as the card is supposed to launch withing the next 10 days, while ATI's chip is scheduled for second half of 2008, probably in the summertime.