Who in the right mind buys a $600 mac for gaming?
The discrete-graphics Mini (2011 version) is a great low-to-mid gaming rig for a television. Mine plays modern enough games (Just Cause, Fallout NV, Portal 2, Skyrim, Arkham City, Dishonored) at mid-to-high settings in Win 7, 1080p on a big flat-panel TV. It is a really nice "console" when coupled with wireless keyboard, joystick and Steam's Big Picture UI.
Expensive, sure, but there's no PC you can buy or build that is even close to as small and quiet, not even at twice the cost. You can make "better" gaming rigs, but they tend to be big and loud and hot and ugly and expensive... and you can't boot them into OSX when you want to use them for other things, either.
I just ordered another 2011 mini from the refurb page ($499) once I saw that the 2012 didn't have a real graphics option.