Apple has released iTunes 11.0.1 via Software Update which includes the following changes:

• addresses an issue where new purchases in iCloud may not appear in your library if iTunes Match is turned on
• makes iTunes more responsive when searching a large library
• fixes a problem where the AirPlay button may not appear as expected
• adds the ability to display duplicate items within your library
• important stability and performance improvements

Apple released iTunes 11 in late November after delaying it by a month. Just over a week ago the WSJ reported this update would restore the duplicate song finder feature.