Tim Sweeney made some comments about their upcoming Unreal Tournament 3 game in a German gaming magazine:
PCGH: How do the general hardware requirements look like?
Epic: Since optimization work is still ongoing, these details may change every day. Generally speaking, the game runs quite smooth with DX9 hardware released by NVidia and Ati since 2006. On high-end cards, including the DX10 models, UT3 runs incredibly smooth already. Additionally, we also support shader 2.0 graphics hardware, with only a few technical limitations.
PCGH: How exactly are you utilizing the functions of Direct X 10?
Epic: Unreal Tournament 3 will ship with full DX10 support, with multi-sampling being the biggest visible benefit of the new graphics interface. Additionally, with DX10 under Vista we have the possibility to use the video memory more efficiently, to be able to display textures with a higher grade of detail as it would be possible with the DX9 path of Vista. Most effects of UT3 are more bound to the fillrate than to basic features like geometry processing. That's why DX10 has a great impact on performance, while we mostly forgo the integration of new features.