Originally Posted by igorsk
Sony Reader can read PDF, TXT, RTF and there are programs (see libpr500) to convert about any other format into native LRF (BBeB). So no, you don't have to only buy books from their store.
How about ebooks for Microsoft Reader?
Looks like books you get from ebookwise can only be read using theirs, which means you spend all that money buying books from them, but should you decide to discontinue using their product, you can't read their books any more.