There will not be a Direct X 10. It will be called Avalon (not sure about spelling). The beta is on Microsoft's site for download. Don't expect it to be out til' near mid 2006.
The X850 XT PE is better, but it was released in January. The 6800 Ultra was released in June-July.
Also remember that the Ultra can be bought for $400 while the X850 cost $700.
The Ultra is also better for overclocking.