Pros:

+ Lengthy if not challenging situations where you have to encourage the best of team cooperation if you are to make it to the safe room alive

+ Large and very well designed levels where you explore almost 80% of the level before you exit. Also encourages the survivors to explore areas off the path to discover hidden goodies.

+ Balanced item placement to allow anyone either on expert or realism to have a fair stock of health and guns each level. Considering the radical and dangerous amount of hordes you encounter.

+ Nice use of some of the more visual features such as HardRain's storm enviroment effect in the bridge section.

Cons:

- Some areas are difficult if not impossible to navigate and you are easily able to lose your way if you're playing it for the first time.

- While radical random horde spawns do encourage survivors to not idle, it has a issue of depleting ammo very quickly and rendering them to rely on secondary weapons too soon or too far from the nearest weapon or ammo cache.

- The Subway finale is difficult due to the small cramped area and little or no support items available. Also once the 2nd wave is defeated and the tank dead. The subway train takes far to long to arrive, and due to the small area of the subway it's easy for a tank or horde to easily wipe them out even before the train arrives.

Conclusion:

In short, this is a campaign designed for those who strive for a hardcore challenge. Those elite L4D veterans who've played expert / realism and keep wanting more. 

And Dead City 2 is designed just for that, large lengthy maps and endless mobs of infected to mow down. This is not a casual custom campaign for those who like to go lone wolf, it requires absolute teamwork or you'll never even make it past the first level.

If you do wish to play this, it's recommended you attempt it on Normal and then try to beat it on advanced or higher.