I just got my ride up and running with a VA kit, and it works great. Use zip ties to secure the ducts to the HVAC case and they won't come off. It blows like ice and the volume of air is far greater than the factory setup. The case is also much smaller.
I have an electric fan and a trinary switch, so it is wired up to send the A/C compressor relay signal ground through the trinary switch and then onto my Megasquirt. The Megasquirt then turns on the A/C relay as needed and controls idle up functions with the IAC.
I did it that way to minimize the current going through the trinary switch and to avoid issues with stalls/RPM drops as the compressor cycles.
The new kits no longer use a heater valve with a relay, the valve is now a low current servo that no longer needs a dedicated relay.