Wow. If these ebooks are tied to a particular device, what if your device breaks and you have to buy a new one? Or what if your device ends up being on the losing end of some kind of ebook format war?
If the publishers do not have a fix for these (common) scenarios, then there's no way I'd buy an ebook reader. I did not realize that ebook content providers were tieing them up with onerous DRM like the music companies did. I'm not against publishers protecting their content, but not to the point where they expect me to pay more, be inconvenienced, or be literally screwed out of stuff I purchased legally just because my device went bad.
Now learning this about ebooks has made me forget about researching any of the features, because the restrictions are too onerous to make even the most stellar device worth considering.