Agreed. I don't know how anybody could use vi with escape unmapped. It's also very useful outside vi though, since esc is the default 'cancel' key in many cases. For example, most browser dialogs (and keyboard-navigable menus) can be closed with esc, and it works for many desktop dialogs too (at least on Linux).
The more common remap is probably capslock->ctrl, for both vim and emacs users, I but I definitely prefer capslock->escape. During normal operation, my left pinky rides the gap between a and escape(aka capslock). Pressing either requires the slightest of deflections to the left or right.
I keep escape as escape as well. Capslock is absolutely worthless to me.
Or use PCKeyboardhack and I forget the other plugin but on a Mac, I have a brief caps lock mapped as esc, but holding it is control. it works effortlessley.
On my chromebook pixel, there is a super/windows key (labeled as a "search" key) where the capslock normally is on a US keyboard. Since I use super as the prefix key for all of my window manager shortcuts, I use xcape (https://github.com/alols/xcape) to allow that key to function both as super (if I hold it down) and as escape (if I tap it).
These sort of systems are a great way to remap keys; I wish such remapping was exposed by operating systems in a nice stock way.
