My answer to this topic from Long and Short Reviews has changed considerably over the years.
There was a time when I had a Kindle but never used it, as I preferred paperbacks. I have no idea why. In any event, as soon as I actually started using my Kindle I became addicted to it. Immediate delivery, no need for bookmarks, all the books I need in one place - what's not to like?
That's not to say I don't value any other type of book. I've bought a number of hardbacks recently because they were signed copies, which are always good to have as an autograph collector. And some books still aren't available as ebooks, so paperback is still an option.
As for audio, I've never really got into audiobooks. I bought the audiobook of Doug Naylor's "Last Human" primarily because I had a crush on Craig Charles, who was the narrator - that's about it. That, however, may change soon, as Totally Bound are working on a project to bring their author's novels to audio, so I'm looking forward to mine being in audio form soon.
So which do you prefer - paperback, ebook or audio?