Maybe Sigurd is right about the examples used by that guy, but if you consider that I think more than the world's half population uses the metric system (including scientists!) I don't see why I should stick to the imperial system.
When I started playing AD&D almost 10 years ago I was so frustrated! And when I began to create my own maps I was also at a loss...I still don't know how long is a mile. I mean I know it is 1.6 km, but I have no sense of the distance...I always travel and see signs in km!
Anyway...I suppose if you want to play traditional fantasy you should use the imperial system (after all Tolkien was English!) Or maybe I should invent my own...which by the way would be exactly the same with the metric!!!