I jumped into this thread very late, so please forgive if I do not quote/reply. I just list my thoughts on the arguments raised.
1) Is it a common practice to say "we do a lot of wonderful eBooks with animations and such"? Unfortunately yes. I say "unfortunately" because they usually do not explain to their clients that those features will work only in iBooks on the iPad. While technicly true that they are creating valid (say) EPUB 3 eBooks, they are not behaving according to professional ethics.
[ Example: my company is producing the first Audio-eBooks in EPUB 3 format, with Media Overlay support ("dynamic highlighting") for reflowable eBooks (not FXL). We clearly stated to our client the limits of the current support, etc. They still decided to accept the fallbacks and bet on future better support. --- You can download some of these EPUB 2+3 from my company website, see the link below ]
4) iBooks is not officially supporting EPUB 3 spec, because they are lacking support for some mandatory parts of the spec, like full MathML (iBooks supports a subset of it), and Media Overlays in reflowable eBooks.
5) Multimedia in eBooks. We need to define "multimedia" and "eBook" here. A decent mechanism of fallbacks might be acceptable on some contexts (say, when video/audio is NOT essential to the rest of the "experience"), while it might be unacceptable in other circumstances (e.g., an Audio-eBook).
6) EPUB 2+3: again, we should define it. If by that you mean "EPUB 3 + NCX", then I have not found a reader yet that refuses to open such a thing. Of course, the "EPUB 3" part should be "EPUB 2 with the syntax of EPUB 3" (i.e., cosmetic differences in the markup --- stuff like <section> should be interpreted like <div>, etc.). --- You can download some of these EPUB 2+3 from my company website, see the link below.
7) I agree EPUB 3 is not the definitive answer to the "eBook industry" needs. And the support to "semantic niceties" is simply non-existing (or very buggy, like in Readium).
Last edited by AlPe; 02-15-2013 at 12:25 PM.