my house is so full of books that my bookcases are layered 2 books deep with books on top of those. they're spilling over shelves and off tables. that was the main reason i first decided to go with an ebook reader - that and immediate gratification
since i got my ebook reader, i've discovered a few more reasons, but the bottom line is i only buy paperbacks if a book isn't available as an ebook and only buy hardbacks of my favorites.
i don't think in terms of tangible but in terms of value to me, and entertainment/pleasure that reading brings me is no different whether i'm reading on paper or my cybook.