I have a Kindle as well as the Kindle app on my phone. I find both to be very useful for a limited, but not rare, purpose. There is no question that it is preferable to read books in their traditional physical form, but this form has one significant drawback: bulk. Books take up a lot of space and are heavy. They are, after all, made from woodpulp. In some sense, we are loading boxes full of wood and lugging them from place to place as we move and then displaying them on shelves.
This, then, is the area in which e-readers excel. When I travel, whether it is the long commute each weekday or longer trips to other parts of the country, having my Kindle and phone along allows me to take along large numbers of books without having to endure the time, expense, and trouble of schlepping a heavy suitcase full of books along.
Beyond the aesthetic pleasures of physical books are the obvious advantages. E-readers then are not in any way a replacement for the books that preceded them, but an enhancement and supplement that allows us to read more books in more places than before.
(I didn't think of a clever way to work in a reference to the inspiring post, so you can just go here and read it.)