I have heard that WPF primitives will not be supported by remote desktop on windows XP. The implication of this is that if you run a WPF application on a vista machine and
We have had no problems using both Remote Admin and Bomgar for remoting once those apps were updated to work with WPF. We've tested XP to XP, XP to Vista, Vista to XP, and Vista to Vista. We'd initially only had problems with tooltips and combo-box drop downs/popups. For the last six months or so, things have been fine.
I just tested remoting into a Vista VM from my XP desktop and our app looked great (if running a bit slow, but it is a VM...) I switched to low quality 8-bit color and the performance problems almost completely went away. The gradiation, etc, was lost on our window background, etc, but it was definitely still usable.
I don't think you should have any functional problems, and only minor performance issues.