Ars Technica (a great publication, in case you didn't know of it) has an article about the problems plaguing eBooks: No universal format, fight over DRM, etc...
If you read the comments section, there are only two universally acclaimed places from which to buy books online: Baen (webscriptions.net) and O'Reilly. And guess what they have in common? Absolutely ZERO DRM and therefore the ability to provide the books in a multitude of formats, including the ubiquitous PDF.
Personally I've been buying and reading books from Baen on my iPhone and computers for 2 years now, and it and O'Reilly are the absolute only two places I buy books from. It's easy, prices are good, and I never have to worry about which device I'm reading the book on.
DRM must go. Check out the author Eric Flint's introduction to the newly-created Baen Free Library in the year 2000, and then his followup rant on DRM in 2006. Publishers and authors have been getting this kind of market research continuously for 10 years now, and they still don't get it. Looks like books are going the way of music, movies and video games (Ubisoft, I'm looking at you): how to best shoot oneself in the foot by screwing the customer.