Had a quick play.
First thing to note is that it isn't a Cycle Journey Planner - which seems slightly odd.
It is based on Ordnance Survey mapping, which still has advantages over Open Street Map in many places away from (well mapped) urban areas.
The big plus of this app is that it will download and store - for off-line working (i.e. away from a reliable signal) - quite a chunk of OS mapping - area chosen by you on screen. This is obviously where you intend to go and not just restricted by current location. It will also show 'places of interest' - inc. bike shops - by distance from centre of screen currently in view.
The levels of zoomable map layers (and the detail of street names etc.) can be set to allow you to cover/store a greater area. Just like having a paper map covering a wide area but not all the larger scale maps for the details.
There is enough storage to cover the whole of Edinburgh at all resolutions.
One thing that some people will find useful is the ability to "draw a route". A new dot appears every time you touch the screen. For a large distance this will be pretty much 'as the crow flies' rather than a Google or other journey planner following actual routes. But you can zoom in to detail precise locations (turns or destinations etc.)
Routes can be uploaded (I think you have to register with Sustrans) and then presumably sharable, but it doesn't seem to be possible to have more than one just on the iPhone.