Why is shutdown so much slower than previous versions?

Solution 1:

Its hard to answer without a full list of packages on your system and possible the console output that normally is hidden by the shutdown screen. However, some bugs have been fixed in the shutdown (I know because I fixed quite a few myself) that make it safer for your data. A lot of services weren't being terminated properly in previous releases, which sometimes resulted in filesystem corruption! 11.04 had a few fixes for this, and 11.10, a few more. I don't think any of the new methods should add more than 10 seconds to the shutdown though.

Perhaps hit 'pgdn' while shutting down to see if anything is being printed to plymouth's log.