Hi Sean
I had an increase of about 10% in my sim when I moved from directx 8 SDK to
dx9. I am not sure if it was coincidence (although I benchmarked my sim
just before and after), just my experience. Note this was on a DX8 game
(i.e. not optimised to use dx9 features).
I play GPL / F1 Champ / netKar / LFS / HL (counterstrike) + UT on occasion
and have had no probs with dx9 (on both of my PCs - Racing + Development
(and FPS))
There are always risks when installing any software, and you may need to
fiddle a little with driver updates etc, but I think on the whole its worth
it. Also, for the sheer good racing I had the other night with netKar
online, I think its worth it for netKar alone. I will be moving Sirocco to
dx9 pretty soon too.
Good luck! :)
All the best,
Ash