This forum has received a question or two a day about it, but so far not enough traffic to warrant the creation of its own forum, in my opinion. One idea I have, though, is creating a post in the forum sticky consisting of a list of XP drivers that are known to work for desktops/laptops that only officially support Vista. As you said, that is the greatest problem with downgrading and to my knowledge there's no list that's even semi-comprehensive. If you or others have your own lists it may be worth combining them in one central location.
Until Microsoft overcome the many Vista issues, downgrading is the only realistic option many people have. In our small IT business we are doing several downgrades every week. Support for downgrading from the big companies varies from poor to none at all, with companies like Sony and othrs just refusing to offer any support for downgrading. The fact is lots of us just like XP and want to continue with it, period. Hundreds of us all over the world spend days looking for drivers and solutions for overcoming the various problems downgrading presents. How about creating a dedicated forum for Vista to XP downgrades? I for one, would find it really usefull. I have done dozens already and feel sure I could save someone out there a lot of time.