Since it was released last month users have been moaning about screen tearing issues and "flickering" when the computer was hooked up to a monitor via HDMI. For once, Apple is not responsible for the screen flicker. It is all down to Intel's HD Graphics 4000 GPU inside the 2012 Mac Mini. Chipzilla has put it's hand up for the bug and said that there is a fix is currently being worked on. While it is not clear when the bug will be fixed, but unlike many Apple problems it has been at least acknowledged.
It is fairly likely that the fix will come in a new software update to OS X Mountain Lion which is supposed to have a number of improvements to graphics drivers (like Intel's Intel HD Graphics 4000 GPU), as well as Airport, AirPlay, and Game Center, among other applications.
The flickering screens is only a problem with the HDMI out; the other two outputs in the Mac Mini, including the Mini Display Port and Thunderbolt drive, are reportedly unaffected.