Apple has released a small point update to iTunes 11 (11.01) fixing iCloud and AirPlay bugs as well as restoring the ability to find and reveal duplicate items.
The iTunes update is available from the Mac App store under updates. We’ll tack more info onto this post as we update the app ourselves.
Apple support download page for iTunes hasn’t caught up (though the listing says 11.01):
This update to the new iTunes 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, and adds the ability to display duplicate items within your library.