I don't regret going Darkside on my Rocket, per se, however, I felt that it was a mistake for me, given my riding style and a strong desire to avoid any accidents.
I am a fairly aggressive rider who occasionally likes to attack the twisties pretty hard and after doing so the very first time, and then observing how that got me scraping rubber off the sidewalls about 2' up from the edge of the tread, I just couldn't find any rationalization strong enough to force me to accept the extra hazard and risks associated with using a car tire on the rear end of this bike. To others, although I would not recommend it, I say, "to each their own".