Comment Not really as "open" as all that (Score 2, Informative) 107
As the Wall Street Journal points out, they're going to be layering Adobe's proprietary DRM on top of the ePub. So even if ePub is itself an open format, it's going to be contaminated by Adobe DRM. (There's still no way to read Adobe DRM'd books on the iPhone/iPod Touch, by the way, unless you crack them.)