This will be long, but I know some people who followed in the past really want to understand how this works. So here goes.
So far my iPhone seems to be working flawlessly. I haven't noticed any issues with syncing. It does delay the syncing, as discussed before, so basically it looks like a 12 hours still has to pass between playing songs to trigger an update to the cloud. I haven't lost a single song from my iPhone though since I started using. I did lose some songs from my iPad but I can't say for sure yet that was the service messing up or not. I got impatient and tired of waiting for the artwork to load on my iPad so I turned Match off and back on for it to load again. The artwork came in but it looks like with the exception of 4 song plays, it lost the rest. The rest were duplicate song plays, as in I played an album from track 8 to the end, and then it repeated the album almost in whole. It got the track 8 to the end, and lost the repeat play of the album. I plan to test in the next few days if repeating the album may have caused the problem, but honestly my guess is more because I turned match off, but I don't know for sure.
Some interesting things happen on the device. I have a 'Recently Played' smart playlist. I can play music on my device, and that playlist doesn't update, except sometimes it does. It makes me worry that something is awry because I've seen in the past attempts with match where this list would actually show song plays and then later delete them and they would never show up in the cloud as played. Right now I've played music today from this device. I also played music last night from my MacBook Pro. My 'Recently Played' list on my iPhone shows none of these plays in the list. It also doesn't show any of the songs I played from my MacBook Pro last night. It shows the last song I played yesterday from this device. Keep in mind the first song I played today DID trigger an update to the cloud for the device and I can see all the songs I played yesterday from this iPhone when I look at iTunes from non-iOS device. So, my "cloud" library as visible from non-iOS devices is completely accurate up to the first song I started playing today from iPhone but my iPhone is accurate only to the last song it synced to the cloud (so the last song I listened to yesterday, which was before I listened to anything from my MBP). So to summarize, my 'Recently Played' list as of right now on iPhone shows all of my play history for my entire library up until the last song it synced to the cloud for the device, which was the last song I played yesterday. Hence it doesn't show in the list song plays from my MBP last night, or any of the songs I played from the device today. I saw this same behavior yesterday. Songs played since the last sync with cloud did not show up in the list.
Another layer: I use CloudScrob to scrobble to Last.FM. This will scrobble any songs it finds in the library that have been played since the last time it scrobbled. I scrobbled my iPhone last night BEFORE I started listening to any music on my MBP. It scrobbled everything from yesterday, so even though the 'Recently Played' playlist on the iPhone didn't show all of my plays and these songs hadn't of course synced to iTunes Match yet (need 12 hours to elaps), they were there waiting to be sent to iTunesMatch and CloudScrob saw them and wrote them. Subsequently, this morning, before I started playing any music, but after having launched the music app on the iphone to see what the 'Recently Played' playlist looked like (it was unchanged from yesterday--still showing the last song I played from the device the day before), I opened CloudScrob to see if it would see the songs I played from my MBP last night (so I could tell if a sync from the cloud had taken place). Even though they didn't show in my 'recently played' list, they were there on the device and I could scrobble them (or not since I already scrobbled them while I was listening to them from the MBP).
So to summarize further, it looks like:
1. Songs played from a non-iOS device always update instantly, which we knew. If you listen to a song from iTunes on a PC, then update match on another PC, the song shows as played. This also looks like it pushes to iOS devices. The iOS device may not show in an smart playlist that it was played, but the device sees it under the hood so to speak.
2. Songs played from an iOS device seem to update after 12 hours has passed and another song play triggers the update. I plan to test if you have to play another song to trigger the update, or just launch the music app, or if it will just happen on it's own after 12 hours. It looks like you have to start playing a song, but I want to test. It would be a bummer to ahve to play a song to cause an update, and even more bummer if you go days before you play another song and your previous plays are lost.
3. Smart Playlists are finicky. At one point I thought they were local to the device, and would always update locally, and then update again after a cloud sync. So as you listen to and/or rate songs, smart lists will update locally, but they won't show updates from other devices until a cloud sync. That doesn't seem to be the case, at least not for all of my playlists. When I rate a song, they disappear from my "not rated" list immediately. This is regardless of what device does the rating. Looks like, as we suspected before, ratings are definitely instantaneous even to iOS devices. However, when I play a song, they don't disappear from my not recently played list, nor do they appear in my recently played list on that local device.
4. An event that triggers the iOS device to send its updates to the cloud library and pull any new plays from the library does happen, but playlists may not update accordingly. They may update "behind the scenes''--need to figure out how to test, but they don't update as visually observable by looking at a smart playlist. My iPhone is aware of the plays from my MBP last night, but they don't show in the 'Recently Played' list on my phone yet, even though they show in it in iTunes from a PC. Eventually the list on my iPhone will actually get in sync (as displayed to me) with cloud, as in what is internally visible on the device will actually show externally on the list I can see.
It's all quite weird but the takeaway is, my iTunes cloud library, as visible from Windows/Mac PCs is always as accurate as the last sync from iOS devices, plus all track plays from any other Windows/Mac PCs as they occur. Your iOS device may not show you externally the correct library. It may be correct as of the last time it synced to the cloud. Some local happenings may externally be visible (like ratings), but playcounts or last played definitely not so much. It does seem to be aware of the changes, and syncs them back to the cloud, and it may actually update the playlists internally, but not reflect that to you externally, or vice versa. I rate songs on the device, and they disappear from the 'not rated' playlist, but they are actually still in it, and when I trip to skip songs, it gets all screwy and plays songs that are no longer visually in the list anymore because I just rated them!
I think the service for the most part is "working" in the sense that eventually everybody gets in sync, but the iOS devices still have some quirky behavior that isn't quite "broken" so much as just doesn't necessarily make sense why it behaves that way. I have yet to have it not update properly, it's just the state your phone may be in while waiting for an update may not make sense to you with regards to smart playlists. I have no idea if they are updated internally and just not displaying the right thing to me in the list, or if they aren't even genuinely updated even though the play data is available on the device.
I don't know why Apple couldn't just have made this something that happens instantly. I just don't understand how what they happen can't be any less complicated than instantaneous updating.
Lastly, aside from syncing, I do see more actual play issues with the service. I never in the past actually had problems playing music, just problems with playcount and last played updating. I've had playback problems this go, from songs playing a few seconds in and restarting repeatedly when they hit that some spot (had this more than once), songs just stopping playing and the app crashing to the homescreen, and songs just stopping in the middle and skipping ahead to the next song (I've experienced this on other streaming services too).
Also, I believe they've stopped it from "timing out" so to speak and making you start a song from the beginning if it has been paused for some unknown amount of time. It seems to remember the play location now.
Don't know if any of this makes a different if you're using iOS 7 or not. I can't see why it would.
