This a review?
I see more opinion than review. Re-flow PDF? The idea is that PDF contains ``pages'', not ``chapters'', ``files'', or what have you. Iff you must have reflowing of PDFs then as an option, for it implies lying to the customer, as in doing something other than what the format was invented for, and hence doing something other than what was expected.
Personally I'd like DJVU support as it is a much better solution than PDF for scanned works (which certainly won't support re-flowing). Some ereaders support it, but not enough by half. PostScript would be a nice to have, for that matter; with proper support it would get you user extendability for free. But DJVU is important for dealing with what in IT parlance would be called ``legacy'' documents: Scanned paper.