I just took a preliminary look at the epub whitepaper and it looks good. It seems to explain things very clearly.
I am very glad when anyone supports and encourages the use of epub. However, I wish that Adobe wasn't so determined to use Flash for their reader software. I don't know why they are so married to using Flash for Digital Editions, but it causes problems, IMO. The most glaring problems are speed and poor integration into the underlying operating system.
The other issue I have with DE is not related to Flash, but with the way that DE is deployed. Requiring an internet connection to individually install and use the application is a very bad thing. How do you install DE on a machine that doesn't have an internet connection? How do you deploy DE on dozens or hundreds of PCs?
Enough ranting about DE. I am happy that Adobe is a prime supporter of IDPF and epub. How about Microsoft, or some other big gorillas?