I've been testing 3DGS on Vista for over a week now. Runs great, no issue at all.

I think some of the problems people are having with DX9 games not running under Vista have to do with the special little "tweaks" many of these games use. 3DGS is very good at following the standards, so I don't see much issue with Vista breaking A6 titles.

A lot of people are confused about DX10. There is a reason they originally planned on releasing it under another name, it isn't a minor change like DX8->DX9. You can't run DX9 games under DX10 but Vista will come with both so you can still play all your previous DX games.