The battery usage is very low. The UI is powerful, but you do need to mess around with it a bit to set it up and get used to it. Setting up the buttons you want to use makes this easier. DEM data works well, but getting the right area takes some trial and error. Track recording does not always record, sometimes it works, sometimes it doesn't. I tried to find a pattern for it but did not see one. It used to always work.

This app was recommended by openseamaps / openstreetmaps. I bought it, but wouldn't again. A very clunky user interface. Downloading offline maps is a nightmare and so far cannot find a useful way to download openseamaps, the whole reason I bought it. Virtually no documentation to work from either. If you want ocean mapping, bite the bullet and pay for Navionics; it works.