I'm not sure how AGS runs on Vista as I have no way to test it so have to go by what others say about how the games run.
I know right now Adventure Maker games run on Vista but have no sound and have some errors .
Shadow from the Am forums was trying to code his plugin to help with AM but didn't have much
luck.
And AM has an installer that you can't change where the files are installed ( users can pick the folder ).
I have a feeling that BestBuy etc will see a lot of people bring in their computers and asking to have windows XP put on them and Vista removed. lol
