I'd call 13FPS over the 8800GT in the same game as you've posted quite an improvement. Plus it's more in the region where it matters and at a higher res, the difference between 153FPS (4850), 155FPS (8800GT) and 178FPS (9800GTX) is negligible, so that test is pretty pointless if you ask me
If that was the defining benchmark for these cards I wouldn't hesitate to get whatever is cheapest.
And may I remind dear Astro that the 512Mb 8800GT OCX is a pre-overclocked card, while the HD4850 is running at it's standard settings...
I agree with Q, a very solid result at a very competitive price point, and we haven't seen the HD4870 yet!