It definitely appears that once you have turned on iTunes Match, the cloud version of your iTunes library is "the truth." From that point forward, the content and metadata of your master library in the cloud is all that matters. That is what will ultimately get pushed down to all of your computers/devices overwriting everything else (including play counts, new artwork, etc). The idea is that anything you change locally in your library will also be changed in the cloud version of your library therefore keeping everything in sync with the latest changes since the cloud would always be up to date. Unfortunately, it does appear that there are certain circumstances and bugs that cause local changes not to update the cloud and therefore local libraries later get reverted back to whatever the "cloud" thinks is the correct state of your master library.The only thing iTunes Match will not do is delete the actual files off of any computer.
The big things that everyone is realizing aren't being updated in the cloud libraries are "play counts", "last played dates", and artwork (I'm sure there are other things that aren't updating properly). "Play counts" and "last played dates" seem to only sporadically get updated in the cloud under many circumstances. As far as I can tell, artwork changes never get pushed to the cloud. The only way to force the cloud to update artwork is to remove the track(s) from your library (and iCloud) and then re-add to iTunes and to iCloud with the new artwork in place. Otherwise the cloud eventually reverts your local library to whatever artwork you had when you first uploaded/matched the files.
Like I mentioned before, there are definitely circumstances under which at least "play counts" and "last played dates" seem to update properly.
Local changes either get pushed to the cloud or they don't. The only fix for when things don't get updated in the cloud is to figure out a method or process which casues the cloud to get updated (if one exists) or for Apple to fix the bugs.
Hopefully, Apple is able to fix the bugs so that ALL local changes on any computer or device are seamlessy pushed to the cloud and then pushed to all other computers and devices. That is how it is supposed to work.
I hope this way of looking at what is happening is helpful to some people…