It is great for being alerted to congestion problems, but many times if you are familiar with the route, you can find optimizations the mapping software can’t.
Yes! Yesterday, driving home from a grocery store five miles away on my usual [fastest] route via the interstate, I told Google maps "home." I guess the AI was having a bad day because it spent the entire ten-minute trip frantically rerouting and giving me new instructions every ten seconds as it tried to route me via city streets alongside and across the interstate's path. I watched the proposed spaghetti-like route on my phone's screen as my car icon cruised along right up the middle. Very amusing. Reminded me of one of those sci-fi films where the robot short-circuits and sparks and speaks word salad.
That might just have been a failure with the GPS -- I've had the same issue before, but the car icon was offset a bit from the highway, so it looked like I was constantly driving on the grass next to it (that must have come as a surprise to the little imps inside my phone doing the navigating).