Well, I called Perrin today and got the answers straight from the horse's mouth.
I should first point out that the system does come with some nice features (flow meter, in-cockpit controller, level sensor, wiring harness, etc).
On the other hand, this system is actually a bit different than the 2d Aquamist setup. The Perrin PWI-1 does *not* use the High-Speed Valve from the 2d system. Instead it actually varies the duty cycle of the pump to vary the output of the system. It is anyone's guess as to how well this setup will work compared to the pump/HSV setup.
The system also does *not* use a manifold pressure switch to initiate the water injection process. Instead it initiates based on the Injector Duty Cycle. I'm going to leave it to more knowledgeable people than I to decide how that fact alone will affect the ease of tuning for the transition from injecting/not injecting.