My SWAG on these results is that the BFG 5700 Ultra held its own for the most part regarding OpenGL performance. The large discrepancy in the Direct3D demos is a more difficult call and one I'll wait on making until I know more. At any rate, these are not representative of game performance and hopefully Humus (or others) can shed some light on things in the near future.
Well... to be nitpicky:
1. The first demo didn't work because of the render targets bit. GFFX cards do not support it, as far as I know.
2. The performance delta is because of PS2.0 speed, basically, and the fact that a 9800 Pro is 8x1 while the 5700 Ultra is... uhhh... 4x2? 2x2?