I have one (an RS), I got it from Wook, I usually leave it off as I'm happy with my mods, but it's fun to play with once in a while, it's not Bluetooth so when you want to use it, you pop the hood and select a setting. Simple to install, and it does pack a punch, only negatives is that the car can feel somewhat unstable when you turn it up real high. Idle, etc.
Happy to answer specific questions