I remap Esc to Caps systemwide.
In Linux:
Create a file ".Xmodmap" in your home directory, with the following content:
clear Lock
keysym Escape = Caps_Lock
keysym Caps_Lock = Escape
In Mac:
Download a program called "KeyRemap4MacBook" and remap tab to Esc.
Using other people's computer becomes a pain in the ass though. I'm such an environment tweaker that I look like my grandma on a standard setup :/