I think there some different things which are important.
first thing there are drivers. new drivers are always good
![Wink ;)](./images/smilies/icon_wink.gif)
2nd thing there are hardware. if you have hardware which support DX9 then the programm should run faster, I think
3rd thing are the application. If you don't use DX9 things in your application, why should DX9 be faster then DX8? It isn't because it is the same thing.
I think: DX9 - DX9 Features=DX8
If I am not right, then said it please.