Having used several apps for accessing OS maps in the UK, I think this one beats them in terms of value for money and in the scope and quality of the mapping (huge range of scales, user-controlled caching, etc.)
My only concerns are that my less computer-literate friends have had some difficulty in comprehending the need and benefits of using the caching. They are not even familiar with the word 'cache', so they aren't likely to exploit it ! It should be referred to in a different way, e.g. 'map pre-load for offline access'. Similarly, the 'setup' aspect and the reference to 'tiles' in the dialogue. I think you should specify an estimated time for download.
Another suggestion - it would be helpful to have a display mode that shows which sections of the map are already in the cache - e.g. by a transparent overlay. This is done, for example in the UK Map app (http://itunes.apple.com/gb/app/uk-map/id365745482?mt=8).
It is interesting to compare the two apps in other ways. As mentioned above, I think iPhiGéNie is more comprehensive. This is probably a reflection of the different licensing regimes in our two countries. Access to some very useful UK maps (1:25000) is free, but others that include essential information (1:50000) are more costly. I hope both countries (and others in Europe) will eventually converge on the best solution.
