When I had a test drive at Bell & Colvill open day last summer I couldn't believe the rev-hang issue. It ruined the car and made gearchanges slow and cumbersome.
I wouldn't buy a car that was so poorly engineered (oops, I did buy an M3W...) If people keep buying the car with the existing issue I suppose it's a bit of a caveat emptor thingy.
But sounds like the car is transformed after the change, so based on my experience I would go for the change in a flash, and treat it as an aftermarket upgrade and you do get a bit more power too.
