We have been working with Direct X 7.0 for about three weeks now, but so far, we have been unable to reproduce the problem with the frame rate decline. But we also did not detect any performance boost, despite Microsoft's claims.  This is what Microsoft had to say about the changes in Direct X 7.

• Increased support for "transform" and "lighting", which should help video cards that perform these functions. GeForce cards should benefit.
• Environment mapping. 
• Runs 20% faster than Direct X 6.1
• hardware 3D sound acceleration for "Direct Music" enabled games
• Visual Basic programming support for developers

  We ran some benchmarks on a system here that we were about to upgrade to Direct X 7.0.  The operating system was Windows 98SE, and the hardware was a Pentium III 450 overclocked to 504MHz, with 128MB of PC-100 SDRAM and a Voodoo3 3000 AGP card set at default clock speeds.  We used 3D Mark 99 Max to test Direct 3D performance. Pentium III SSE optimization was enabled.  Here are the results.

Direct X 6.1 with previous Voodoo3 drivers (1.02)

800 x 600 x 16bit = 4753 3D Marks
1024 x 768 x 16 bit = 4502 3D Marks
1280 x 1024 x 16 bit = 3326 3D Marks

Direct X 7.0 with previous Voodoo3 drivers (1.02)

800 x 600 x 16bit = 4761 3D Marks
1024 x 768 x 16 bit = 4504 3D Marks
1280 x 1024 x 16 bit = 3330 3D Marks

Direct X 7.0 with new, DX7 Voodoo3 drivers (1.03)

800 x 600 x 16bit = 4707 3D Marks
1024 x 768 x 16 bit = 4478 3D Marks
1280 x 1024 x 16 bit = 3321 3D Marks

  These numbers are virtually identical, the differences are statistically insignificant.  While we can see no reason not to install Direct X 7, we also can't see any compelling reason to install it either. We did not see any performance boost, even though Microsoft claimed a 20% improvement. It may have benefits when future games are optimized for it. 

                       Dr. John

Microsoft's site:  http://www.microsoft.com/directx/