Using the final 2.2 version om PMIII, I still had to copy the dialogFileStacking.xml file from the default Blue2 skin to the Project Mayhem 3 folder to make stacked files playback correctly.
Also there is a small visual problem with the new MP-TVSeries v2 plug-in. The quick-select near the bottom that shows "All/Unwatched/Latest/etc" does not display correctly.
Also noticed that the "My Radio" was not displaying the net-radio stations I had setup after updating to 2.2. Copied the Myradio.xml file from the previous version of PMIII and it was fixed.