Autodesk will be announcing official details on Microsoft Windows Vista support for AutoCAD and AutoCAD LT in the next 2-4 weeks so please check www.autodesk.com/autocad for more information. In the meantime, please note that no official statement has been released yet.
Personally I have been running Windows Vista on many of my own machines new and old as well as my TabletPC and love it and knock on wood not a single crash in about a year of beta testing it. A very nice OS. Now I have to get back to playing the new free Windows Ultimate Extras released yesterday like the Texas Hold 'Em card game.
Windows Vista Official Microsoft Team Blog