The extra turrets nicely beef up the firepower of the otherwise rather lackluster vehicle firepower, making it much more of an option for fighting and exploring.
The turret hit points are a bit low for the later stages of the game, and spitters will quickly destroy them. However, the mod allows you to carry spares in the trunk that will be automatically be equipped. Turrets will also automatically reload with ammunition in the trunk.
It's great fun! But IMO the rocket ammo is a bit cheap, and you can get 1000 rockets in a stack (100 packs × 10 rockets per pack). Might feel less OP if 5 times the cost and only 100 rockets per stack — but I won't complain too much :D