In addition, to deal with the issue that programs others than vi may require the use of arrow keys, I use Autohotkey on Windows to map Caps Lock + hjkl to the arrow keys! Thus, both in vi and outside(, in Word, say), I just use Caps Lock + hjkl to navigate. Thus, I never have to move my hand away from the "home" position to use the arrow keys.

I did that and it is actually incredibly easy to get used to (within a couple of hours). The bigger thing you have to get used to -- and which I suspect most will struggle with -- is not moving around when in insert mode.

hjkl may have started because the Joy was working on an ADM3A that had no home row, but the elegant and efficient consequence is that your hands fingers do not move from typing position.

you just have to map your tab key to escape to get the original layout back[1].

[1] http://en.wikipedia.org/wiki/File:KB_Terminal_ADM3A.svg

What do you use in insert mode?

Escape. Normal mode is for navigation. :)

I'd like to have your willpower!