Thanks to GLFW (great tip-off from dek) I got an XBox 360 controller working very nicely with the game.

Owing to how GLFW works I had to replace my lovely Mac-specific application launch code with a much simpler (and cross-platform) C file that uses GLFW to create the window + OpenGL context so that I could hook into it's input functions.

Much nicer now plus there's the added bonus that more of it should work cross-platform now.

I'm not quite sure how reliable the controller joystick and button mapping will be for different controllers - only got the one so not an easy thing to test right now.