I'm really quite happy with this announcement. It may not be ePub 3.0, but if it truly does support HTML 5 then it's pretty darn close.
I don't know if any of you have seen the material available at the
Khan Academy, but it teaches everything from basic arithmetic to calculus and differential equations (as well as various sciences, history, finance, and other subjects). It does this through short videos (well over 2,000 videos) and automated drills.
I'm currently writing a book on algebra and I'd love to include something similar to what Khan does inside my book, because some people learn better through auditory lectures, and everybody learns better through practice. HTML 5 will allow me to do this, so I'm quite pleased with the announcement.