Valve is pissed at all of the benchmarking "optimizations" they've seen in the hardware community;
- Half-Life 2 has a special NV3x codepath that was necessary to make NVIDIA's architecture perform reasonably under the game;
- Valve recommends running geforce fx 5200 and 5600 cards in dx8 mode in order to get playable frame rates.
- even with the special NV3x codepath, ATI is the clear performance leader under Half-Life 2 with the Radeon 9800 Pro hitting around 60 fps at 10x7. The 5900 ultra is noticeably slower with the special codepath and is horrendously slower under the default dx9 codepath;
- the Radeon 9600 Pro performs very well - it is a good competitor of the 5900 ultra;
- ATI didn't need these special optimizations to perform well and Valve insists that they have not optimized the game specifically for any vendor.