I used Carplay for the first time a few days ago and I can't say I was thrilled. My biggest issue was that you can't use Google Map through your phone, and while your phone is in CarPlay mode, you can't use the vehicle's native nav. With Apple Maps still being a gigantic pile of shit, this was a pretty big deal.
You also can't disable individual features of CarPlay. Its all or nothing. Again using Maps as an example, if you're traveling to another country and don't get data on your phone, you can't disable that one part of the software. You either get a big blank screen with Apple Maps (no data) or no CarPlay at all (to use the vehicle's native nav). Also theres too much drastic screen switching from Apple to native and back to control various features vehicle features.
I'll need to play around with it more to get a better understanding of the system, but from first impressions, if I were to own a car with the feature, I would NOT use it, and you know what they say - The first impression is the last impression.