Apple has released an update to iTunes (version 11.0.1) which fixes a number of performance issues, notably the abysmally slow searching in the initial version of the program. The update also brings back the Find Duplicates command, which was, apparently, forgotten in the initial release. If you were disappointed in searching with iTunes 11, download this update and try again. For me, the searches that took more than 30 seconds with the initial release are nearly instantaneous now.
It’s worth noting Apple’s description of the update:
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. This update also includes other important stability and performance improvements.
The fact that it mentions “searching a large library” shows that Apple does, indeed, care about those of us with large music collections.