Vista is a pain in the ass to communicate with XP machines, but not sure if XP has been officially patched to make it easier yet... I needed some other protocol on all of my XP machines to allow it to communicate properly. Once it is set up it works quite well though!
But why would microsoft make it easier for XP to work with Vista when they want people to be exclusively on vista?
I think you hit the nail bang on the head there... It is crazy though, MS must be making a killing... The place I work has to buy any new machines WITH VISTA PRE-INSTALLED and then pay again to downgrade to an XP license... Madness.