Steve,
I would guess that all of my assist is gone by about 40 mph or less. That being said, even at 20mph, my steering feels exactly as it did before. People assume you lose road feel when you have assist but that's not the case. You always have normal road feel with the EZ PS system. The transition from assist to no assist happens so gradually and seamlessly, you really pay no attention to it. Even with full assist, it always feels like it did before, just lighter. I think it's perfect the way it comes out of the box but if you wanted the assist to stay in longer or be gone sooner, you could do that quite easily. In fact my plan was to modify the VSS in order to have the assist phase out sooner. Then I drove it and immediately decided that would be a complete waste of time and effort!
I do have one criticism of the EZ Electric system. The VSS they supply is an ugly, horrible looking thing but they refuse to just leave it out. It belongs in the trash. Milwaukee Speedometer Service has a very nice VSS that replaces the angle drive unit on our ZF's. When you're ready, I'll give you the specifics.
Dave