I think Apple went for "too simple" first gen carplay. As I said my Uconnect unit is fantastic and I have no idea what kind of OS is under the hood, but it works great even with Apple devices.
I've read and seen so little, I don't have an informed opinion; though I have high expectations -- perhaps too high. Having iOS Maps displayed on screen and third-party apps like Overcast accessible would be great to me. If Audible has a CarPlay app, that's my trifecta while driving. And having used all manner of standard USB and BT interfaces from Ford, Chevy, Hyundai, and Toyota in rental cars, I can't imagine it would be any worse. Those are pretty basic.
At this point, I'm really just waiting to see if this is a real Apple product. Or one of their distractions they launch and forget about a year later. It's looking more like the latter, presently. But that might be due to conservative auto-makers who only stand to lose money on overpriced, under-performing Nav packages from CarPlay and Android Auto.