I will try to respond to the issues as I perceive them. Clearly not from an engineering point of view.
You do lose the GPS for the time of the override, since the car thinks it is stopped, but it only takes a couple of minutes to program in where I want to go, and frankly, if I don't know where I am going, why do I care where I am? Seriously, this is a very minor annoyance, since I am usually on the Interstate or turnpike when I decide I want to know how long it is going to take me to get somewhere.
Haven't noticed any glitches or oddities in the electrical system.
Goes on with the volume control.
If I ever had any electrical issues that I were going to take to the dealer, I would take the unit off before I got near the dealership.
Frankly, I have only used it a couple of times since I installed it, but I don't like being treated like the village idiot, particularly when I have been rear ended by a lady on the phone while in rush hour stop and go traffic, because she was "distracted". She denied even hitting me, but since her Mercedes was red and my Prius was white, it was fairly obvious. When they make people stop shaving, plucking their eyebrows, putting on makeup and holding a phone to their ear with one hand and a cigarette with the other hand (and I guess steering with some other bodily appendage), then I will gladly remove this override.