I think there is one major aspect of the benefits offered by eBooks which printed books can never compete with: dynamism.
Unlike a dead-tree book, eBooks can change over time. One way that happens is through publishers releasing new versions of the same book. Depending on the software/hardware involved, you may be able to get the updated version, or only those who download it after the update will get it - but in any case, a new version is available without re-purchasing the book.
However, a form a dynamism which I find even more interesting is through metadata or as we like to call it, “Subtext” - because that’s the name of our app which is built entirely around this idea. Subtext allows authors, experts, and everyone else the ability to enhance any eBook with contextual information, videos, notes, polls, etc.
I’m biased, of course, since I work on the product, but I honestly believe reading with Subtext adds a ton of value. More importantly it exemplifies an aspect/benefit of eBooks which seemed to go unmentioned here, so I wanted to call it out.
Subtext is currently iPad-only and supports the ePub format, including DRM eBooks purchased through Google Books. I agree with many other comments here that DRM, as it briefly did with music and currently is with movies, causes far more trouble than it is worth and hopefully will live a short life.
On the DRM front, I’ll point out that J.K. Rowling recently launched pottermore.com where one can purchase DRM-free eBook versions of the complete Harry Potter series. She is using watermarking as a deterrent to piracy, which is an interesting approach. The industry is watching to see how that experiment goes and it may likely influence future publisher decisions around eBooks and DRM.