Good for Mike. He only had one more season left on his original three year deal, and this apparently wipes that final year out. It would have been better if they could have waited another year to see if he could carry success into another year, but the media would have been all over his lame duck status and he has proven that he is a good head coach. Extending his deal also continues the Packers recent policy of extending existing contracts for players (and now coaches) who deserve it. However while most player contracts are not guaranteed, I bet his contract is. He probably saved himself a big chunk of money by not using an agent too.
At the bottom of the article he mentioned that offensive coordinator Joe Philbin will get to call the plays during the Pro Bowl and step out from McCarthy's shadow for one game.