How do I update iTunes Match info on my iOS 7 device?
I turned off iTunes Match on my phone. All the Match songs that were downloaded were still available (cool!) and the non-downloaded ones were no longer listed. I then killed the Music app and rebooted the phone. Same thing. I then turned iTunes Match back on. It re downloaded all the metadata, but reattached to all my downloaded songs. It didn't need to re download them.
Pretty awesome.