We have posted some ePub samples on the AZARDI resource page to enable publishers to possibly understand and evaluate the various transition issues when making decisions about when to move to ePub 3, and how.
The samples include four Gutenberg books processed as ePub2, ePub3+2 (transitional) and ePub3 directly out of IGP:Digital Publisher. I could have added a KF8 mobi as well but that would have been showing off, and AZARDI doesn't like them.
The most interesting issue with these ePub variants is how they work on various readers - the reason for this evaluation set. It helps to set a baseline of understanding the issues.
Cover treatment is probably the biggest issue, but ePub 3 also has a cute little landmarks section that will only be seen in AZARDI right now.