TechwareLabs has published an article titled ATI and Nvidia Says "No Support for Vista".

Microsoft Windows Vista has been out now for more than 6 months. At first ATI was praised for supporting Vista and Nvidia was criticized for not supporting their products. Quietly however ATI and Nvidia has not been providing drivers for mobility/Go customers. I can hear you saying "You're Kidding Right" nope but I wish I was. Complete lack of support for Mobility and Go owners for an operating system is unacceptable. We are not talking about Windows 98, ME, or 2000 here. This is Vista, the latest offering from Microsoft.

ATI and Nvidia Says "No Support for Vista" Article