What @evowrx said. I smashed one in my gc8 with their 11lb flywheel. I was mostly attracted to it due to the price and it seemed like an affordable up grade.
Drivability is not the worst I've ever encountered, however it is a case of no engagement until the last 20-30mm of the peddle throw and it is reasonable hard to make a smooth start without shudder. I'm personally not worried by this, but I can see how others would not be able to live with it.
I can't comment much further as iv done minimal mileage due to the car still being a work in progress, have maybe out 200km max on it. I'd like to think it will hold the power I'm aiming for (200wkw) and will handle abuse. My advice would be to consider other options if you want/need something that's feels drivable in a daily.