I only ever really made a couple of runs with the "Turbo" button.
I was talking to somebody the other day, and it came up in the conversation.
The big issue is that you have NO SPEED CONTROL WHAT-SO-EVER when you directly connect a motor to a bunch of batteries.
It's just a matter of what speed you are doing and which gear you are in while you hit the turbo. I was working on a single long, straight stretch of road with a higher speed limit than the 72V Metro could do.
You are FAR better off with just a higher voltage PWM DC motor controller.
I didn't have one of those, and am just a little crazy, and had the parts to make the turbo-by-pass, so what the heck!
It was fun, but never was built into any sort of final design.