I have upgraded to the latest Amarok in -Current last month (it was included in -Current since March 1), but today is the first execution of new Amarok (2.2.2) and i was to see that my playlist are gone . Perhaps the new version breaks some incompatibility with the older version and the result is devastating. Let's hope that it won't break again when 2.3.0 is included in Slackware-Current.
By the way, Amarok 2.2.2 is definitely better than previous version. It doesn't hang again when i opened the main window. Creating new playlist is also faster and smoother than before. Other than that, i think you can see it on the Release Notes.