Use an Xbox controller with a Mac

You HAVE to use it wired (USB). The Xbox 360 uses a proprietary wireless protocol, so your computer's Bluetooth antenna will not work with it.

I ran into the same issue with my laptop.

Update: I just reinstalled the Tattieboggle drivers and tried my wireless over USB. The driver informed me that the wireless controllers only operate on wireless, even when plugged in! It said I would need the wireless dongle (an oxymoron if I ever heard one) to use that model of controller with my laptop. I hit the guide button with it plugged into my laptop and it immediately synced into my Xbox 360.

So yes, you must use USB - either with the dongle or a wired controller. If you do want to buy a wired controller, look at something like the Razr Onza (which is well reviewed from what I hear, I have not used one yet; it is also cheaper than an MS controller).

In Windows it works out of the box, but if you install this software the Xbox 360 will display a battery indicator on the screen.

In Ubuntu, the Xbox 360 controller works flawlessly with xpad. (I've tried this successfully with a wireless controller)

In Mac, I've found a driver here, but I haven't tried it because I don't own a Mac myself.