I just did the upgrade on my 2017 CX-5. I've tested with Android Auto for the first week, using a Galaxy S9+. I did not have any issues with Waze or Google maps placing me in the correct location, or recalculating my route.
A few days ago, I began using it with an iPhone 7. I found that on quite a few occasions, the maps struggled to place me in the correct location. It was about two or three blocks off sometimes. This was the case no matter which map app I was using (Google maps, Waze, Apple maps). I can confirm on at least one occasion, Waze would not re-route me while using Apple Car Play. These issues never happened while using Android Auto.
I believe the issue is with cheap GPS hardware in the iPhone. When I looked at the iPhone, it says "GPS signal lost", something I've never seen in the 6-months I've owned the Galaxy S9.
Not that you asked for a review, but overall, with the exception of the GPS issues, I like the Apple Car Play experience more than Android Auto. Mostly because you can use the touch screen in Apple Care Play (while the vehicle is moving less then 5mph), while the touch screen is always disabled in Android Auto.