Good idea, poor execution

If the idea of meeting up with the Survivors from Left 4 Dead 1 really excites you, you're probably going to be disappointed by The Passing. The idea had lots of potential, but the way Valve executed it leaves much to be desired. You only see the other Survivors twice throughout the entire thing, and there are only 3 chapters to play through. The interactions between the two groups of humans is pretty dry, and each of the original characters (except for the one that is considered dead) only seem to have one or two lines.

Despite the poor integration of the first group of Survivors, the new content that comes with The Passing might be enough to warrant a purchase. One of the biggest additions is the Mutation game mode. Every week Valve creates a new special game mode for Mutation that is played either in single player, campaign, or one of the online modes. They come with unique and sometimes crazy rules that create a new experience for everyone. For example, at the time of this writing the Mutation is "Chainsaw Massacre", which takes place in Campaign mode and has all four Survivors using chainsaws with unlimited gas. There are also two new weapons - the M60 and golf club - and a new uncommon common: the Fallen Survivor, who drops items when killed. The new and unique dialog in The Passing is humorous and very fitting as well. Oh, and there's a new Midnight Riders song, and it's fantastic.
 
The Passing may be much better than Left 4 Dead's Crash Course, but it's over before you know it. Thankfully the Mutation game mode is probably enough to warrant a purchase. Just be prepared for disappointment when you realize that the inclusion of the original Survivors seems more or less like a hook to get people to buy the DLC.