I'm using iBooks, Kindle, and QuickReader. But each is missing a crucial feature that my favorite reader supports: Instapaper. Instapaper lets you create folders (and then export entire folders as ePubs); easy text selection and copying; dictionary lookups; tap links in the book to open a simple browser; "like" books that toggle an external bookmark system (I use Pinboard) and perhaps the killer feature, automatic scroll.
IOW, I want an Instapaper for ePUBs and DRM books. iBooks comes close, but the clunky organization and super-slow load times make me cranky. Bluefire Reader's text options are not optimal, and I can't click links. Quickreader provides the scroll, but no links, and no text selection.
I just checked and "ePub reader" returns 100 items in the iTunes Store.