I installed this unit in a 2011 Prius with a non-JBL stereo. First, the good: It greatly improved the sound quality through the stock speakers. The two custom equalizers can tailor the sound to your preference if the other built in EQs cannot. The bass boost really kicks up the bottom end performance. The DVD, USB and micro SD sources provide plenty of options for playback and sound great. The screen is fairly responsive, but could be better. Changing modes is pretty snappy and the rear view screen is good using the excellent Sony rear view cam.
The bad: The user interface (UI) is not the best. Function buttons are small and can be missed if there is any movement from the car. The radio station buttons are bigger, but only three are in sight at a time, unless you go to the "set channel" screen. To see the other big buttons you must swipe the screen to get them in view. The navigation is inferior to any Garmin unit, IMO. If you drive off the current route, this unit gets totally confused and insists on returning to the original route instead of rerouting. The map is less detailed than Garmin units, also.
The Supertuner III is not quite as sensitive as the stock Toyota radio, which is somewhat disappointing, but at least it is close. Bottom line: The sound quality is very good from this unit, but the quirky interface and navigation detract from the overall satisfaction with the 930BT.