One of the first things I upgraded when I bought Black Thunder. Next to no functionality. I've heard even taking calls was hit and miss with the factory unit.
I suffered with the factory unit and a bt to fm transmitter for about 2 weeks. It was horrible. There seemed to be constant interference and the audio quality was garbage. Soooo happy with the final results of my install. Ended up having no alternator whine. And ive got my doof doof back.
Edit: and the fact i got the facia kit for $300 was a bonus. If you need one, and want it cheap, sign up for autobarns membership. It gives you 20% off your first transaction. Its meant to be up to $50 but the guy who served me applied it to the whole order. I wasnt about to correct him lol