in the middle of testing RR under vista myself.
I previously tested RR in vista that was being run inside of vmware and everything worked ok.
I now am testing RR in a standard vista install and there are a few small issues. Havnt completely figured them out yet but i think they are mostly hardware related.
RR seems to only run ok if you turn aero off, which kind of sucks but in a car environment it likely wont matter which windows ui you have.
My volume slider in RR dosnt work in vista, but this is likey because of the complete rewrite of how audio is done in windows and plus a slight driver issue.
I think RR may have to look at the way audio is done and make some changes.
other than that it works fine. RRConfig in vista instantly opens, where in XP it always takes a while to open for some reason, not sure what the deal is with that.
I definitely intend to put vista in my car.
Some of the new features will be really nice inside the car.
There are some small issues people likely will have most of them hardware related, so your millage will vary.
but i do think its about time also to start talking about it, i know some others here have been running vista a lot longer than I.