I did not really understand what you were talking about there with the pull quote. I understand there are issues with big pictures etc on certain devices as you mentioned, that being said, I personally don't like all those devices with its quirks. I think that the market for eBooks is in Android/Apple/Microsoft tablets, laptops and AIO screens in libraries etc, all of which have or will have great software for reading ePub3 publications.
I am currently reading a book called "Tuesdays with Morrie", a very good book by the way, on my Xperia Arc S. It is in PDF format and I just scrolll it down as I go, I really don't see myself using eBooks latest features introduced in ePub3 on such a small screen, it's just not the experience i'm hoping for in such a small screen.
If we start with the assumption I wrote above, then responsive design is important as your screen size can vary from 7" to infinity (:P)
^_^