I recall the first time I saw familiar territory on a 1:50 000 OS map; land that I thought I knew well in its 1:63, 600 guise seemed stretched, less concentrated in its complexity, barren, almost. This artefact of enlargement, caused because the move to metric hadn't been accompanied by much revision of the data, took a while to overcome. Metrication made sense mathematically but to someone who's map-reading had been honed (OK, subjected to slight improvement!) over several spotty-faced years poring over the familiar density of the old 'one-inch' maps the newcomers were an unwelcome intrusion.
Sometime later I saw my first 1:25 000 map whilst walking in one on Britain's National Parks and I couldn't read it. It was as incomprehensible to me as a text written in a non-Latin alphabet. I can only suppose that my previous internalisation of the 'one-inch' format, which had been to such an extent that I could take-in a scene and imagine the ground lying before me, was sufficiently complete to be completely confused by the unfamiliar details, and space, on the super-scale impostor.
The relevance of all this? Well, all maps are approximations, compromises between the real World in all its dimensions and the paper plane created by cartography. All I had done was to embrace one such approximation and map it onto my mind, forsaking all others. It was a skill, but not one that was as easy to transfer as might be expected. Whilst the 1:25 000 map is a wonder of cartography (although desperately in need of revision), giving the walker hitherto unexpected detail of his surroundings anywhere in the whole of Britain, I still find the 1:50 000 easier to empathise with (my middle-age eyesight certainly no-longer finds the move from 1:63 600 such a pain) and I think the reason for that is context.
I was investigating fancy GPS gear with downloadable maps and realised that one would still need a paper map (and a compass, of course!) in order to make sense of the few square inches of illuminated LEDs. The 'bigger picture' that shows the lie of the land, that puts our place in a wider expanse, that reminds us that it is an appreciation of the whole that truly makes sense of the particular spot in which we are located, is what makes the 1:50 000 map such a treasure.
Oh, and if the option existed, I would still prefer a 'one-inch' map, with contours in feet and, preferably, at the same price as they were 40 years ago!
A fascinating site on the development of OS maps - http://www.fieldenmaps.info/info/
An excellent source of downloadable (£) OS mapping - http://www.mapyx.com/