I've used it for six years now and wouldn't be without it.
Just make sure your phone has a lot of storage to save off line maps. Without having your maps saved the app is pretty much useless in most back country. It also allows you to keep your phone on airplane mode to conserve your battery. My iPhone has 256 gb of storage so I can save a lot of maps. It takes a long time to download maps even with a good wifi connection.
That's my problem. I often have to delete maps of other areas to make room. I suggested to them to set it up so you could store maps on an SD card but so far they haven't done it. That would be a huge improvement. With that I could store vast areas in the highest resolution.
