I played this to completion when it first came out, but didn't own the game. I picked up a copy of the GotY edition today because I wanted to play through on a harder difficulty, and also the challenge modes are the kind of thing it's fun to come back to every once in a while for 15 minutes of fun (which can easily turn into 2 hours).
This is an awesome game and I can't recommend it enough for people who haven't played it.
A couple gripes about the GotY edition: * My saves and progress from the original version are not compatible. I'm guessing this means that the leaderboards for the challenge modes will also be separate. This is a big disappointment, as I won't be able to compete against my friends who have the original version. * The 3D is a cool gimmick, but not quite cool enough for me to want to play the whole game that way. I turned it off after about 30 minutes.
Again, I highly recommend this game if you don't own the original, but can't say it's worth picking up if you already have Arkham Asylum.