Timing is always a crap shoot, there are many variables. My wife and I have been to Vermont twice. The first and second weeks in October seem to be when the leaves are at their peak, starting in the "Northern Kingdom" and spreading generally southward from there. Last year they had not had much moisture, which the locals said dulls the colors, nor had they had any frost. It was still pretty, just not as brilliant as 2001.
I would recommend staying on the smaller side roads. There are only a couple of interstates anyway, but we found the small roads less busy and more interesting. If you are camped in a central area, you can access any part of the state in a day using your T.V. The whole state is small in size, and also very rural. We were not camping, so don't have any reccomendations there.
In terms of how busy it is, I found it not as busy as some of the stories I had heard. Most of the traffic seemed to be in the commercial shopping towns. (Orvis, etc)
This is a trip I highly recommend, we thoroughly enjoyed our time.