I think I've accidentally discovered the solution to get play counts updated quickly, and in sync across devices.
The short of it, I upgraded my MacBook to Mountain Lion last month, and recently, something happened that caused my iTunes Library to get so messed up that I needed to retrieve a backup copy to start over. But this time, I decided to start with a fresh new library, and once I did this and turned on iTunes Match, it started behaving much differently than before.
Basically, iTunes Match now starts automatically updating itself once every 5-10 minutes if I have music playing, but, unlike when you manually select "Update iTunes Match", it seems to go through this process much quicker. Because of this frequent updating, all my play counts are not only updated quicker, but also syncs across all my devices. For instance, last night, I played a song on my MacBook at 12:53 A.M., and after iTunes Match automatically updated itself shortly after, the play count was updated on all my devices (iMac/iPhone/iPad) at 12:55 A.M. Similarly, when playing a song on my iPad at 12:57 A.M., it updated on my MacBook almost instantly. (Albeit, the duplicate play count issue still exists in iOS devices.)
I initially thought that Apple was changing something on their end, but I wasn't seeing this behavior on my iMac (running 10.6). Similarly, I wasn't seeing it happen between iOS devices. My MacBook had to be running iTunes for everything to sync. I then initially thought maybe it was a Mountain Lion thing, that maybe the iCloud performance is just better under the hood. But after starting a guest account and turning on iTunes Match, the behavior still wouldn't replicate.
Finally, after doing some research today, I discovered for the first time that there's iTunes Match local cache data that can be deleted within iTunes. I wondered if deleting and resetting this on my iMac would replicate my MacBook's behavior and, sure enough, it did. Now iTunes Match is also automatically frequently updating play counts on my iMac. Here's what I did... (naturally, back up, and do all this at your own risk.)
1. In the Advanced section of Preferences, delete your iTunes Store cache. Chances are, this probably doesn't do anything for this problem, but I just want to make sure things are as fresh as possible.
2. Turn off iTunes Match, but do so while also holding down the Option key. If using Windows, hold down the Shift key. This will delete the iTunes Match cache data.
3. Once iTunes Match is off, sign out of iTunes. Then sign in again with your Apple ID.
4. Turn on iTunes Match. Because the local cache has been deleted, iTunes is essentially re-scanning your entire library like it did the first time. Depending on your internet speed and library size, this might take a while, so plan accordingly.
Once it's done, try playing some music. If it works, you should see iTunes Match attempt to update itself, within 10 minutes or so. Once it does that, you can check your other devices and the play counts should be updated accordingly. The only caveat is that it seems the 12 hour rule still applies on iOS devices, but any thing you play on your Macs will still very quickly display on all your devices.
It seems as if Apple is making some nice improvements under the hood (which might explain the recent problems), but apparently I needed to clear out my local cache (which I haven't ever done, and I've been a subscriber since launch) to see some of the changes. Hope it works for you.
