A friend of mine uses it on his iPhone and this year I used it on a Galaxy. I was really impressed at how well it worked out in the field. I used a compass to understand how to point the phone to line it up with where I was. It gives you the ability to save the maps for the areas you'll be in so that when you can't receive a cell signal you can still use the GPS to see your location.
I love my OnX maps app. I used it extensively this last season. When packing out animals it was extremely helpful being able to use the saved satellite imagery. It’s not nearly exact as a GPS but it let us plan out the route as we went, in a snow storm, in the dark, on two different occasions.
It’s also extremely helpful when you hunt anywhere near private land boundaries. It will let you skirt right along the edges of private land.
I will be using it excessively while I am on my mule deer/elk hunt on the salmon river this upcoming season because the unit is a jumble of private and public lands.
The only place that this is lacking is the more remote counties that haven't upgraded their gis systems yet (Western SD) ..... When there you won't have landowners on your map... I have asked on x about this and they said it is getting better as the counties upgrade....
I spend a lot of time using the maps on the home computer. You can mark areas/items of interest on the computer and they will download to your phone. Pretty easy on the phone, but even better on a large PC screen.
I sold my Garmin right away (3 years ago) and have never been sorry I did.