The reason I'm interested in ePub is for scalable fonts. Yes, i can zoom in on pdfs but then i need to scroll over to the left and then to the right, left then the right, repeat till you have to scroll to the top of the next column. It gets pretty frustrating after a while.
Also, ePub (when done correctly) breaks down files and makes it easy on a phone or tablet. A 96mb file like core book can be frustratingly slow to flip threw.
I do understand the limitation of tablets in ePub but as someone who just wants to read threw the main set of rules, i can look at them later (in the actual pdf file)