Music and video may not work in
fiction and genre fiction books but I would love to have those options in some of my non-fiction and specialty books. Some great examples (for me):
The Complete Beatles Recording Sessions: The Official Story of the Abbey Road Years 1962-1970 - This book could never be an effective ebook for me without some type of multimedia. There is a lot of text but there is also a wealth of photos. This book could be enhanced greatly with additional audio from studio time, interviews, etc.
Design Like You Give a Damn: Architectural Responses to Humanitarian Crises - Yet another book that would be horrible as an ebook without multimedia additions. Architect interviews would be a great addition to this book, along with site videos, elevations, and [of course] color photo.
I think that when you guys think that ebooks don't need innovation - most of you are speaking of novels and non-fiction books that deal with 99.99% text only (maybe a couple of diagrams tossed in for good measure).