Well, I've been using it for the past week and a half, and I have had no problems whatsoever.
But really though, if it ain't broke don't fix it. That's my advice to you skeptics out there. Wait a few months and see how testers and other people are doing with DX9 and make sure it is absolutely stable before installing it.
I'm still using 30.82 Detonator Drivers for my GeForce 3 Ti200 card , because their new 40.xx drivers are horrid for my card. Just proves that not everything new is reliable.