I use it all the time to lock my truck if I think I may have forgotten to do so.
In my opinion, The most useful feature is the ability to find a place on the internet such as restaraunt or even trail head coordinates using your phone and paste them into the navigation in the app. Then you just click "send" and it send the location to your truck. When you get in the truck your nav is ready. Beats punching stuff in manually on the dash.
After the trial period you are unable to see the "vehicle status" which shows your fuel and tire pressures etc, but you retain the remote key fob and the nav functionality.
Data breach would have to be at onstar, which is what the app is ties into. I suppose that's always a possibility, but the chances that somebody is standing next to my truck and has the time to hack something like that is unlikely. They're more likely to use a crowbar
I've attached images of the interface. For this trailhead of this forest service road, it would be very difficult to punch this into the in dash nav and find it. The app makes it easy.
Send to maps if you use apple car play
Send to in dash if you want it on the dash nav