All this will depend a lot on what, how, when and where you read. I don't read in bed much, but when I do, I find holding my Opus much easier than I would holding a hardback. (But I never read harbacks anyway. Hate them.) Mostly I read in the métro or train, and for that the Opus is much better than paper.
For reference books, I think paper still wins, especially for me since my Opus does not have a search function. I suppose this will change some day, but publishers need to come up with well-designed e-books, not simply digitizing books that were designed for paper. I think the whole design of the book, probably from the writing stage, will have to evolve.
For books that require quality images, again paper wins hands down.
But for books made up mostly of text that I read from beginning to end (most of my reading), I don't miss paper at all.
When I have to read in paper, if it's a good quality paperback that I can carry in my handbag, I still enjoy it. But I have discovered, since I read e-books, that the print quality of paper books varies a lot, and some can be very bad. I had never noticed that before, but maybe it's just my eyesight getting older.
