What's new:
1. A complicated and comprehensive software vertex clipper
2. DirectX pixel shader 1.1
3. Better CPU frame buffer support
The software triangle/vertex clipper is a very big deal, together with the existing Force Software T&L feature, it should get rid off almost all the geometry problems for most new video cards (video cards that were working slightly better with Force Software T&L feature on).
Pixel shader feature is another very big deal. Version 1.1 is just enough to support N64 combiners, and is widely supported by any DirectX 8/9 video cards. If your video card is DX8 or DX9 compatible, you will be very happy since almost all combiner problems should be gone.