I have a few hundred ebooks. Some of them I only own in ebook format; others, I have in multiple formats but have read more often in ebook than in all paper forms combined. (*cough*Cryptonomicon*cough*)

I'm glad I can now carry around The Hobbit and The Lord of the Rings without having to find homes for, at a minimum, four mass-market paperbacks or one mmpb and a beefy trade paperback....