I'll add that the Garmin doesn't need to be connected to a phone in order to get you from A to B; it's basically just a sat nav with a few other bikey things thrown in. You can search for villages, towns or cities; or addresses (but you have to know the house number and post code so it's not always easy); or intersections. Then it figures out a route in a few seconds, from wherever you are, and you follow a little line all the way to wherever you want to go. If you miss a turn it re-routes like a car sat nav... which is cool if you happen not to like the road you're on and you fancy exploring one that looks nicer. You can set it to 'road', 'gravel' or 'mtb', and you can choose 'avoidance' options like less hills, no main roads, etc.
Once or twice it has tried to convince me that motorways are okay for cycling on.
It also steadfastly refused to let me leave the bumpy, pedestrian-heavy 'Cuckoo Trail' en route to Eastbourne, and once even took me through a field on Road Cyling mode. But these have been rare problems (and all part of the adventure, I guess)... annoying as they were at the time.
Mostly it's been pretty well-behaved; I've done 5k km since I got it for xmas and I've used it for a bunch of all-day rides that would previously have taken me hours of route-planning.
You can get an app that stores all your rides and keeps track of loads of stats, if that's your thing. I use it to save particularly scenic routes, and to count how many kilometres I've done over the weeks, months, years.
It also guesses how many calories I've burned as I ride, which I'm sure is wildly inaccurate but has nonetheless done wonders for my cake habit.
Batteries last for a good long time per day; I always charge to 100% before a long ride and have never reached less than 35% by the end of play, usually 6-8 hours riding (so not epic epic audaxes but enough for me). You can get extra battery life by using an external battery that attaches to the underside of the mount. I guess that way that internal battery would last a lot longer too. Not cheap though.
So there you go - I got a bit carried away writing this but hopefully it's all helpful : )