As a teen myself, i perviously owned a d3 and it was an ok unit. First off, the navigation system was by far the worst thing Ive ever experienced. For example, when you are searching for a POI you can not sort by distance, there is no Text-To-Speech, and the avic has the dumbest routing logic and it will take you far and beyond just to get you some place close. Also having to deal with the nav disk bothered me.
On the other hand, the avic was flawless in every other department. The on screen ipod function is much safer than using the ipod simply because it is bigger on the touch screen display. The videos will not work with the 6 gens (useless you roll back the firmware) or touches, this didnt bother me to much because I dont watch while driving. Otherwise everything works well on the unit!
HOWEVER, I know this is a AVIC forum and probably get some bad feedback, I recommend the Kenwood units... from my experience they are so much better than the avic units. The nav is 1000x better, you can add POI, you can play videos from ipod (all gens) and their tech support 1000x better and they send out updates in a reasonable amount of time.