Please do consider including everything from the outside front cover to the outside back cover - and everything in between,
One of the reasons that PDF as a format has been so hugely popular, is because it is widely recognized, usable with minimal fuss, and supported features that almost every type of ebook could use. This includes text, image handling, search, TOC, indexing, etc. Until ePUB has all or more of the same features, it cannot displace PDF as the defacto standard. However, ePUB will not acquire these additional features until, and unless, their is a demonstrated need for them to be included.
No matter which format you plan to use, eventually its capabilities and limitations are recognized. Consumer reaction, positive or negative, has the most affect on manufacturers. Since the publishing industry is using ePUB internally, eventually anything any of the other formats need will be supplied through ePUB.