Something I don't get about the Firefox developer tools is why they make the console logging unavailable if I've defined console as a window level variable, overwritten for the purposes of extending its behavior.

This only happens for the Firefox tools. Firebug, Safari and Chrome web inspector don't care. We do this so we can enable and disable console statements for debugging purposes. We monkey patched console, and because of that I can't use Firefox developer tools at all. It's a shame.