Sure, you know all the usual reasons. Carrying an entire library in a reader the size of a thin paperback? That's pretty heady stuff.
Being able to search for a part you wanted to look back at simply by keying in a few words rather than diligently poring through the entire book. Oh yes, that counts.
Being able to buy a book online and read it immediately? Definitely.
But I think one of my favorite parts of reading digital books (and dislike watching other people reading digital books) is the anonymity of it. I can read anything I want and no one will turn their nose up at what I'm reading. I can read a book 4, 5, 6 times or more and no one will say "Haven't you already read that?" Because they can't tell what I'm reading. (Conversely, because I like seeing what other people are reading, this works in reverse, too. I miss out on being able to strike up conversations about other people's books. Instead, the conversation tends to turn to the reader itself). Still, I do like that whole secretive aspect. I like feeling a bit mysterious.
So, if you too read digital, what is your favorite part of the experience?