I used to hate reading on the computer but the Kindle app changed that somewhat. It makes it easier to navigate the book, you can adjust text size, it automatically recalls where you left, etc. For trivial stuff like biographies and such, I love it. I can just sit in my studio, magnify the text a bit, grab my guitar and practice scales and such while I'm reading.
It's also nice to have all the tools at your fingertips to look up word's definition or to check a wiki entry about something. Sometimes when reading a regular book, there's some things I'll simply let slide.
That being said, sometimes, I wish I had both a printed version and the Kindle version.
And for anything which requires more attention like philosophy or history books or such, there's just nothing like the real thing.