If vim is your choice of editor, you may feel that you need access ESC a lot of times, but it's far top left to reach, induced heavy inconveniences. So I thought mapping ESC to Caps Lock would be great, but I found a greater solution swapping Caps Lock and ESC at http://superuser.com/questions/16070/vim-command-to-map-capslock-to-escape/19518#19518<p>Check the link to get real. And it works <i>at least</i> for Ubuntu 9.04, I've no idea of others, though I think there must be an working around for them. Try, and enjoy!
I prefer swapping Caps and Ctrl. I use Ctrl-[ instead of hitting Esc. It's an extra button press, but Ctrl is a more generally useful key (screen, C-c, etc.) in that location.