Well, I played a game recently that used all eight directions as screen directions to move on an isometric grid, and it was a very odd control system which I never totally got the hang of. The eye tells you you’re moving up the screen, but your brain tells you you’re moving diagonally across the grid, and your finger usually hits the wrong key, at least that’s the way it worked for me. YMMV.
As for which way is north, I tend towards upper-right as well but I have a sneaky suspicion that left-handed people might tend to disagree with me, so it’s probably better to make it configurable! That kind of thing is bound to have a biological bias of some kind.
EDIT: Make that a biological/cultural bias. I wonder if it’s tied to the direction in which you read text?