MountainCat: Great questions. Sorry for the slow response! But I'm doing about 75% new and 20% old.
* About 90% of New Mexico will be new (there are so many alternates).
* About 90% of Colorado will FEEL new (because it was mostly snow covered when I went through in May - so I'm counting that as "new").
* About 75% of Wyoming will be new (Yellowstone and Wind River will be new).
* About 50% of Montana/Idaho is new (part of this is due to fires forcing me to make a new routes).
In short, I suspect at least 75% of the trail will be new stuff! And that's exciting! That's why I had few doubts on the return.
In fact, even in the sections that I had already done (e.g., around Helena, MT), I found it fun to predict what was going to be around the next corner. I was amazed how much I remembered and how much I forgot!
Maybe I'll see you at the finish line around Halloween 2007!