Picked up an extra new copy to collect a couple days ago, at $7.80. It's even a little cheaper today. If anybody has been waiting to pick up this game, I recommend grabbing a copy now. Very enjoyable, and has one of the best single-player DLC add-on's I've seen (Pigsy's Perfect 10).
@Movie Monkey I played it several months ago, so I don't remember exactly. What I do remember, though, is that it wasn't just a slapped-together cash-in that rehashes stuff from the main game. You're playing as one of the supporting characters from the main game, and he has different moves, weapons, and tactics. It's also more than a couple hours long (if I remember correctly), and just seems really well done. It was like a fresh take on the world of the first game.
Pigsy's Perfect 10 is almost a prequel of sorts as it takes place before the main storyline. You are controlling Pigsy so obviously the gameplay is different than when you were playing as Monkey. It's more stealth based as you can't use the big guy to take out a bunch of mechs in hand to hand combat. He does have a zapper that can stun the mechs if they get too close but it's use is limited. Other than that there is a sniper rifle and some other useful gadgets for dealing with enemies. The voice acting is just as good as it is in the main game (although it is mostly Pigsy talking to himself and his robot buddy) and the length is pretty decent (5-6 hours maybe....I can't remember as it's been a while since I played it) I need to go back to finish off some achievements at some point. It really is a very well done add-on to the game and the story kind of gives more meaning to what Pigsy does in the main game.