>* Everything Ford makes has a bug where the car's computer will lock for a minute or two and either crash / decide the phone doesn't exist or display a blocking modal dialog telling you that you have too many tracks on your phone if you connect it using USB. I have ~11K tracks (iTunes Match) and that's apparently more than they tested with. Toyota had a similar failure with USB.
>* Bluetooth is more miss than hit: pairing is usually buried in the UI, slow, and reconnects are unreliable so you might have to try a couple of times before anything connects.
Bluetooth pairing seems to work just fine on my family's Ford Fiesta 2016 (using the simpler version of Ford Audio). Once done for the first time, it only takes a few seconds after I turn the key and they're working together. Occasionally sound cuts off for a sec or two if I have the phone in my pocket but I blame it on my ole' Galaxy S3 and CyanogenMod drivers.
Have you tried it with USB? That's what I had all of the failures with but I've heard that was a problem with the older Microsoft stack they reportedly weren't happy with. The cars I rented were either 2014 or 2015 model years.
I've rented a fair number of cars while traveling in the last year and hit a number of problems:
* Everything Ford makes has a bug where the car's computer will lock for a minute or two and either crash / decide the phone doesn't exist or display a blocking modal dialog telling you that you have too many tracks on your phone if you connect it using USB. I have ~11K tracks (iTunes Match) and that's apparently more than they tested with. Toyota had a similar failure with USB.
* Bluetooth is more miss than hit: pairing is usually buried in the UI, slow, and reconnects are unreliable so you might have to try a couple of times before anything connects.
* None of the cars have a UI designed for more than a handful of tracks so while you can get something to play eventually, the experience is terrible.
* Not everyone supplies enough power to charge over USB or does so inconsistently, so you may arrive with 10% battery if you used the GPS.
100% of vehicles with AUX in lines work perfectly every time without any fussing. I want something like Bluetooth to work but there's this massive market failure where almost nobody seems to have a QA team or a support process where updates actually happen (BMW suggested that a friend buy a newer car to fix their bugs). I'll give Subaru an honorable mention for having reliable software but they desperately need to hire some UX specialists.