Quite recently I released a small article discussing if you (as a developer) should upgrade to Vista to take advantage of DirectX 10 functionality only available in Windows Vista. Quite simply the answer was “yes” in my article. As a developer you should always take advantage of new technologies, specially if that technology will replace an existing technology.
HotHardware.com has released an article more aimed towards the end-user than the developer which discusses the State of DirectX 10. In this article both performance and image quality are evaluated to give a fair estimation.
It’s 13 pages long but worth the read, check it out at HotHardware.com.