Honda is the worst. In two different Hondas, I had to make sure I didn't plug my phone into the blessed USB port to charge, otherwise the wireless AA connection would drop 20 minutes into the drive and I'd have to re-pair manually. And wireless would crap out every hour or so.

Mazda was wired-only, which was fine since my phone was new at the time. But Android Auto was clearly not designed for Mazda's otherwise very good non-touchscreen HMI.

Both Hyundai/Kias I've rented took a solid 90 seconds to pair every time I got in the car.

In a Chevy I rented, it would either pair up instantly and work perfectly or it wouldn't pair at all, depending on the alignment of the stars or something.

BMW's implementation worked great, too bad the rest of the controls in a modern BMW are idiotic. And also I can't afford one.

I've had several Toyota/Lexus loaner cars. Those worked fine, to my recollection.

Maybe I'm cursed, but at this point I don't particularly care. My real, honest-to-god experience with smartphone connectivity in cars is this: the most reliable, user-friendly, brand-agnostic experience is a bluetooth adapter shoved in the cigarette lighter, and a phone holder on the dash.