I'm planning to do this unsupported, in early May 2008. The dates are flexible. The costs depend on whether we camp/picnic or go for hotels/restaurants, and that depends on who comes along and how they want to travel.
My main purpose is to get practice/experience in organizing and leading a tour group (something I hope to do for a living in a few years.) So part of the test is just seeing who shows up and making sure everyone is happy. It might be a cheap eats/camping tour one way and then a 'luxury tour' on the way back. (You can take the train for the leg that you don't want).
Most of the route is fairly easy, and so far most of the people who've expressed an interest are beginners, so you can expect a slow, easy pace.
I started a blog to cover the tour and the preparation for it, and I've posted more details there. (The link should be in my signature at the end of this post.)