Don't know the status of the GT-R or other PDK/DSG-type transmissions on the automatic downshifts. However, on our 7AT it's really more of a help than a hinderance. If you're actively managing your downshifts you'll be hitting that button way before the TCM does it for you. The TCM downshifts at a pathetically low RPM just to prevent a long-period loss of lockup (or for that matter, engine shutoff eventually) due to low RPMs. If you're not actively managing downshifts (e.g. coming down to a red light in normal everyday street traffic), just let it do its thing and it'll keep you in the right gear for a very mild and fuel-efficient takeoff when traffic starts moving again
