I put a mid-range Kenwood head unit in my road trip car last year. So far only one person has been able to figure out how to pair their phone to it over Bluetooth (the instruction manual is in the glove compartment; doesn't help). The Bluetooth audio skips. The audio jack requires no set-up, works 100% of the time, and never skips.
Maybe that is more the fault of the head unit than anything else. Several years ago I bought and installed an aftermarket stereo which could play mp3s from a usb stick. I think it was a Kenwood in the $150 - $200 range. I recall being stunned by how horrible and behind-the-times the UI and menus were. I thought "all they had to do was copy the iPod menu layout" (or any other decent mp3 player).
That and other experiences with car infotainment systems have lead me to believe that any electronics that go in a car are at least 5 years behind their non-automobile equivalents.
This move to Bluetooth very much seems like planned obsolescence. In sure in a few years all the issues people have with Bluetooth will be "solved" by a whole incompatible spec.
The only problem with the 3.5m jack is that it's too cheap, unobtrusive, and reliable. You can't brand it, market it, or upsell it.
