It is a fun add-on, just be warned that you cannot coordinate with your teammates while this is active. It might be better to have an option to push to talk to the survivor that is different from your normal communication key, otherwise you cannot give your teammates commands without tipping off your survivor.

Another fun add-on I've played with are Perks servers. Survivors and Special Infected both get to choose from sets of perks which change up the gameplay a bit. Here are all of the perks I can remember off the top of my head:

Survivors: Martial artist- no melee fatigue and runs 10% faster. Demolitionist- starts rounds with an explosive and can carry up to 2. Revive teammates in 3 seconds and they get back up with 10 additional health. Default health is 130. Chem Resistant- Pills give you an additional health boost. Reload 30% faster. Shots do an extra 20% damage.

Special infected- Hunter: Leap 20% farther. Pounces automatically do at least 9 damage. Secondary swipes do 5 damage. Pounced swipes do 2 additional damage per swipe. Move 50% faster. Boomer: Booms call more zombies than normal. Boomed survivors cannot see their HUD, and vomit recharges 20% faster. Move 10% faster. Smoker: Secondary fire releases smoked survivors and snare recharges faster. Smoke range is 20% longer. Tank: Tank moves 30% faster. Tank punches and throws rocks 30% faster. Tank spawns with 1000 additional health.

These are rough estimates of what I remember, the point is that you have to choose from a pool of these when a round starts, survivors get 2 perks from 2 different pools and SI only get 1 per infected type. This is obviously a big departure from a normal server, but I think it is a nice change of pace for those of us that are getting bored playing the same matches all the time.