Hmm. I wasn't sure where to start with this one. As a book lover, I'd never thought much of the eBook concept and would rather have just not thought about it at all, frankly.
However after looking at the Project Gutenberg site I can see the merit in such a thing - I even read the first paragraph of The Raven by Edgar Allen Poe online... But I still don't think I would use them myself.
Audio eBooks are different - they don't involve reading a computer screen - so although I've never listened to one, I might one day if I ever need to drive over long distances alone.
So why don't academic libraries use eBooks more? I'm guessing price, copyright issues, licensing, lack of appropriate titles?.... This article about their use in academic libraries explains in more detail.