The Passing and The Sacrifice had potential but never went anywhere far with it. I do love my golfclubs and being able to be the original survivors again though.
Dead Center has like the primary Scavenge map but is just a common city and lacks some atmosphere.
Dark Carnival has all the atmosphere that Dead Center lacked and so much more. Is pretty awesome.
Swamp Fever is interesting but hard to navigate and why are there so many zombies in the swamps?
Hard Rain has all those unnecessary witches that adds variety and takes place in a cool setting. It disappoints me though how Valve ditched the randomized night/day & weather affects though, since the torrential rain adds a great mood.
The Parish has The Bridge. The Bridge is awesome. Great way to end the campaign's storyline. Loved the environment and the mood of the city. + Bombing is win.