In reply to Deleated bagger:
Doesn't look bad, although I'd prefer if they included at least OSM as an option. With the 1:250K default basemap, I can't really assess the app's speed and usability with something detailed like 1:25K vector maps without buying a license first. And their map store selection is very limited outside UK, sadly. Not much Alps - no Swiss, no Austria, just IGN.
But I was quite surprised to see they charge money for map licenses that were released by governments for free use long ago. For example Norway and the US. Charging $30 for a map you can download for free seems a bit excessive. Sure, there is some overhead in collating the data together, but $30? The free OS OpenData maps are missing as well (although I am not sure about their license terms).
What I do like is that I can import custom data in GeoTIFF or other formats (as a paid upgrade). Could be a nice option for using these digitised Soviet secret military maps (which are still surprisingly accurate for some more remote regions) or other sources. But again, can't demo the usability of that, unfortunately, without paying (big detailed GeoTIFF scans can be quite taxing on phones). A trial time-limited version of the paid features would be nice.
Seriously, I am now considering using Locus. It's Android only, which is a big hurdle for me, but at least they seem to stay up to date with open data releases (they just added the free Swiss detailed dataset) and seem to be community minded developers.