We've had a Garmin for several years now. When she's good, she's very very good. Other times, she's an exercise in frustration and patience. We call her Garmeana for a reason. She (the voice) sounds so put out when you turn off the recommended path to get gas or a meal, and she says, "Recalculating." When you finally reach your destination it would be nice if she said, "Congratulations, you made it!"
One caution -- updates aren't automatic, so if you're traveling through recently completed road construction, you may be on your own. Just keep going, and she'll catch up sooner rather than later. Usually. DH does have GPS on his cell phone, so that helps. One night we were looking for a particular store and followed Garmeana's instructions to the letter, only to find out the store was no longer in business so it didn't do any good to follow directions.
Garmeana usually wants to guide you the shortest distance, even if that means skipping the more convenient freeway. That said, she's really helpful in rural areas, much easier than trying to follow a map after dark.