I have not used this yet but plan to start by replacing asphalt driveways for the lots to this type of system and gravel. My park is in northern Maine. Some of the biggest benefits of the system are its resistance to frost heaving and ability to drain away flood water and in winter, needs less deicing compared to asphalt and concrete surfaces. Not to mention the maintenance and installation cost savings.
Depending on how the driveways go, I may convert my overflow parking (asphalt that needs replacing) with this system. I too am curious if anyone has gone this route yet. Specifically in the northern areas.
I would prefer to keep things simple and just use plain gravel. Adding truegrid seems like it will just introduce more problems if it heaves. The KISS principal rarely goes wrong.