What device is giving you problems?
I have an iPad 2, and iTunes Match seems to be working fine.
I also have an iPhone 4, and Match is a MESS. All of the playlists on the phone are blank. I can select the playlist, but there are no tracks in it. It looks like songs that were previously downloaded are still there, but I couldn't download anything new. So, then I tried to turn off iTunes Match, only to find that I can't! In iOS 6, it apparently has to get turned off in 2 places in Settings: App Store and Music. I've tried to turn it off in both places, tried loaded songs directly from iTunes on my computer, tried restarting the phone several times, but nothing works. The Music app still shows all those blank playlists. What a mess. Has anyone else seen this issue?