I have used it for a short period of time and had no probs. (Played Unreal2, MOHAA, Unreal2003, Splinter Cell)
Pros
1.You'll be ready for the games that aren't here yet.(Splinter Cell recommends it but is not required)
2.You can run 3DMark2003 to see how truly outdated your video card is now before the DirectX9 games hit the shelves.
Cons
1.Unless you have a Radeon 9700 (or from the same series), your video card can't use most (or all) of DirectX 9 new abilities.
2.You CAN'T uninstall DX9 (well you can...format hdd, or use old image
)
Theres plenty more I'm sure but I quit fooling around with it when I scored the big 13XX on 3DMark2003 with my sys (see below).
<A HREF="http://forums.btvillarin.com/index.php?act=ST&f=41&t=421&s=205efc501496823a64ba7fbd37152ff2" target="_new">Psyko's Rig</A>