One of the frustrations people have had with Windows Phone 8 is the new Xbox Music. The older Windows Phone 7 used Zune, which has now been replaced by Xbox Music. Unfortunately, the old Zune playlists aren’t directly compatible with Windows Phone 8 or Xbox Music. There is a solution, however. You can browse to your Zune playlists and rename the extension from .ZPL to .WPL, which will make them accessible in Windows Media Player, and from there you can sync to your phone.
You can usually find your Zune playlists under C:UsersXXXXXMusicPlaylists, where XXXXX is your account name on your PC.
Syncing with Xbox Music is still clunky compared to the old Zune experience, but hopefully Microsoft will improve it with time. My biggest issue is syncing songs that aren’t a part of my Xbox Music Pass or songs that weren’t bought in Xbox Music.