I'm not sure if you're expecting a response from the dev's with some kind of usage data, or if you just want people to post their general situation.
In case of the latter:
I'm a college student, and I use Digital Editions because the ebook versions of my textbooks are considerably cheaper than their physical counterparts. I saved around $150 this semester in book costs, and I don't need to lug around a bunch of dead weight :)
I can't wait until ebooks become the norm, and the world's youth can kiss back problems goodbye! Oh, that and saving the rainforests and what-not.