Kinda a tangent, but can Kindle books be stripped of DRM yet? Even if I bought a Kindle, which I have no desire to in its current state, I'd never buy a single book off Amazon until I knew the format could be opened up to allow me to take my purchases to another eReader if I bought something after the Kindle.
The great thing about the iPad / iPhone is you have access to dozens of different eStores including Amazon's, B&Ns, Borders, Apple's, etc... even still, I see no point in purchasing any kind of book media from a store using a format that hasn't been cracked, and is able to be read in good apps.
I'd prefer keeping all my digital books in a single app, such as Stanza (iBooks is lacking some nice features that Stanza has), rather than splitting my library between 5 or 6 apps, and having to remember which store I bought which book from. Plus they'd all be in an open format, so if for some reason I couldn't use Stanza anymore, I wouldn't have to jump through hurdles to get my collection working on another app, like I would if my books had some kind of DRM in them.
I cannot fathom how it is legal to sell books that can only be read in a single eReader device. It'd be like if the music you bought online only worked in a single music player.