I saw on the news about a HS in Clearwater, FL.
Interesting idea. I am a big fan of the Kindle and this idea makes financial sense. I saw one article that stated that books cost $300 per student (not counting novels they have to buy). While not all textbooks are available on the Kindle (and some probably are not going to be very good unless you go with the DX). Chemistry books for instance could be a challenge on the Kindle (I think the diagrams would be better on the iPad--much more expensive).
A big upside is that the Kindle allows for someone to read a book and when you come across a word you do not know, highlight it and a definition pops up.
The downside is that lugging around those books at least gave the kids a little more exercise!