ATI has brought a new update for its Catalyst drivers and software suite. It would seem that in response to NVIDIA's release of the GeForce 7800 GTX - hence, claiming the performance crown - they have included some noticeable performance improvements in popular games, as noted in the release notes:

Enhancements to our driver's internal memory management bring significant benefits to 64MB and 128MB framebuffer configurations in Catalystâ„¢ 5.7.

The resulting performance gains are most apparent in high resolution, everything on modes, when running applications that use a significant amount of graphics memory. Examples include:
5-15% gains in 3DMark05 on some products
20-60% gain in Far Cry Regulator across multiple settings
25-60% gains in Half-Life 2 at 1600x1200 4xAA 8xAF
40-60% gains in UT2004 at 1600x1200 6xAA 16xAF
50-100% improvement in Comanche4 at 1600x1200 6xAA 16xAF
50-200% gains in certain ShaderMark tests at high resolution

These figures come directly from ATI, so unconfirmed for the time being. The new release also packs fixes for several game bugs including Flight Sim 2004, Trackmania Sunrise, and Warcraft III.