I had a similar skepticism about the things. Having had a hiking GPS for years, I did not expect the automotive version to be a big boon. Boy was I wrong.
While driving around, I have looked for nearby attractions (parks, museums, etc.) and have found lots of interesting stuff. Of course, I don't fiddle with it while actually driving ......
My Garmin has led me astray a few times though - it picks routes, on occasion, that seem the "scenic" way, whether set for faster route or shorter distance. It has once gone haywire and directed me in the completely wrong direction. I think you have to broadly know where you're going to be absolutely sure.
I will be off to Superior (Provincial Park to Marathon, maybe beyond, very soon. You are lucky to live in an incredibly scenic area - best part of Ontario for sure!
Jaan