Interesting, I am heavily using CarPlay since beta 4. I drove over 2500 km since then and I've run into 2 minor issues.
1. CarPlay disconnected after phone became hot, but I didn't report it as it happened only once.
2. I think since beta 5, the North in the Apple Maps got locked and the arrow representing car, wasn't always pointing up, which IMHO is worse for drive orientation, but not a deal breaker.
I could set the directions from the CarPlay Calendar App, I was comparing the directions between Google Maps and Apple Maps and both were showing effective. Maps also diverge me twice from the original road when 2 major traffic jams occurred while I was driving. I was using Siri to set coordinates via voice commands (not quite accurate but I blame my accent 😉). Adding route stops during a ride worked flawlessly, also I've had no issues with reporting hazard situations, etc.
I am always installing from IPSW, if it is worth mentioning.