For the Mac users out there....be aware that even though it says it's for PC AND Mac....it doesn't mean it'll work as you expected. The reason why I gave it a good rating is because it does what it's supposed to...granted you have the right software. There's a driver out there for this controller if you google search 'xbox 360 controller driver'. Download that, and you'll get the driver.
The main problem with it, is that the driver reads the controllers as digital, so it doesn't read in analog signal. In other words, the controller won't work well with first person shooters. It DOES however work well with perhaps an emulator for Sega, Nintendo, or other old games, which only use digital readings.
This controller does it's job, but there just aren't any good drivers out there for this controller, if you want to specifically use a controller for your emulators, I'd look for something cheaper. If you do choose to get this controller for like Call of Duty or anything like that, get the right driver and play around with a button mapper. (yes it is another application). A button mapping application will let you set the buttons to any kind of keyboard or mouse command from your computer.
Buy Xbox 360 Control Pad 3 Controller!