Certainly, there's much more info to come on ePub for the iPad. Here are the questions that are important to me as an academic researching emerging educational technologies:
1) While it's nice to know that I can bring .epub volumes into iTunes and subsequently synch them to an iPad, I'd really like to know about all the options for getting them into the iTunes.app. Drag and drop into a yet-to-be-seen "Books" Library in the iTunes.app seems minimal. So, what else? How about podcasting? I can already podcast audio, enhanced audio, video and PDF files so why not simply add .epub to the list of podcastable file types? This would make sense because podcasting is the mechanism for resource discovery and distribution used by Apple's iTunes U. An iTunes course containing eBooks or eTexts in the ePub format seems quite natural to me.
2) Will Apple enhance the ePub standard? They did this with RSS for the iTunes app and iTunes U, so why not here as well? Extensions to the ePub standard would only work on iPad and be ignored elsewhere. Extensions would add functionality such as bookmarking, marginal notes and so on. Is Apple planning to do this? It would make sense if they are as that would be a boon to self-publishing teachers and learners.
3) Yes, there's more to this than simply tapping into the Gutenberg Project and reading books in the public domain. The ePub standard makes it possible for anyone to publish without the intermediation of commercial publishers. This completes the revolution begun in the 90s with desktop publishing and laser printers. Today, anyone can create a digital novel, collection of short stories, textbook, magazine, newsletter, newspaper, etc. and publish it worldwide. The iPad and other devices capable of rendering .epub completes the circuit.