There are some very helpful iTunes Match tips in the second half of this Wired article:
I restored my up-to-date offline library and left this machine without Match enabled for a few days while I looked up how you reset your iTunes Match account. And that’s where the fundamental problem with the service rears its head: you cannot reset it.
I contacted Apple to find out if this was true, and it is. Fact of the matter, I was told, is that Match works fine for most people, so hard resets — which would then require time-consuming rematching and uploading of local songs — aren’t an option.
[continue reading at the link below]
For my problem, lots of duplicate playlists, the solution was a bit simpler:
- deauthorize all computers that are using iTunes match (note this is just PCs or Macs, not iPads/iPods/iPhones etc.
- setup a clean iTunes library (nothing in it) on a computer
- re-authorize that computer to use iTunes match
- let it synchronize
- deleted the duplicate playlists
- update iTunes match from the menu bar of that computer
- volia, the playlists should be deleted from iTunes match and the changes should get pushed out to all devices (iPods/iPads/iPhones/iOS)
*Note: before you reauthorize iTunes match on additional PCs/Macs (beyond the clean one mentioned above), you will probably want to delete any redundant/unused playlists from those computer BEFORE you reauthorize… otherwise their unwanted playlists may make their way back into iTunes match.
More resources on these topics: