ePubs are scalable - They are not designed to be viewed on any particular device or screen, unlike PDF files. The screen size doesn't matter, and the formatting should be the same. The fact iBooks is terrible at ePub files is a seperate issue... Really, it's an argument over whether an ePub designed for any device is viewable in iBooks without hackery.
On the iPad, chances are that ePub would look fine in any third-party reader.
Last edited by dorino; 10-09-2011 at 05:57 PM.