I ran into some wonkiness last night with the Playlists. I have many of my playlists in folders. I was trying to create a new auto-playlist within an existing folder. I right-clicked on the folder name, then selected New-->New Auto-Playlist. This brought up a dialog box where I could name my new auto-playlist. Within seconds, this dialog box disappeared before I could actually type a name, and it took me to the settings box for that new auto-playlist. So I went ahead and set the parameters for the new auto-playlist and hit Save. Then I checked my playlists and the new auto-playlist that I just created did not exist.
So I navigated in Windows Explorer to my playlists folder and discovered that MB3 had created a blank xautopf file in my playlist folder, which essentially assigned my auto-playlist settings to the playlist folder (which I didn't know was possible). The only way I could get rid of theses settings on the playlist folder was to close MB3, delete the entire folder in Windows Explorere and then reopen MB3. This was reproducible. The only way I could create the new auto-playlist that I wanted was to do it in MB 2.5.