I can't stop playing this game. I'm 65 hours in, was done with the "story" after 20, and I've just been picking away at the islands getting to 100%.
Just as a bit of an aside, I had a kind of interesting moment of exploration when I visited the northwest island (You know, the one that blows up every plane that tries to land on it). I went there, before the mission that takes you there, and I just explored around. Seeing all the weird towers everywhere, having it constantly rain, and have these crazy guys come out of nowhere trying to kill me was kind of awesome. After getting thoroughly creeped out, I grappled the first flight out of there. I realized how awesome a myst-like game could be with the mechanics of this game. How cool would it be to traverse Myst with a grappling hook.