I've played it and I can tell you that it's an awesome game. Honestly, it's not in the same league as the first 3 but it's definitely better that the forth. It consists of 5 episodes, the first two are so so...but the remaining 3 make up for it.
I agree with narcossintese that Telltale is the only company (besides lucas arts) that I would trust to do this game justice. They are ex-lucas arts employees after all. However, maybe some of them worked on FullThrottle, Day Of The Tentacle and Grim Fandango but the person who is actually responsible is Tim Schaffer. And you can tell while playing the game that a person like Tim Schaffer or Ron Gilbert (creator of monkey island), who's talent can make the difference from a great game to a "classic", was not involved.