Because the mini had no music on it at all, I set it up to use the cloud for music; thus, I can see on that device exactly what has or has not made it up to the cloud.
My current iPad had music on it already, and I had set up Remote to point to the laptop. I turns out that if you redirect iTunes to a different directory, Remote will follow right along (Remote is thus following a softlink, rather than a hardlink to whatever you pointed at when you set it up). The decision at implementation could have gone either way, and I think they did it the right way, altho R. notes that it has caused him some consternation on occasion.
In any event, Remote can see what I've uploaded as it is uploading: it's a true, current window, which is nice. None of this caching and getting out of date and re-syncing nonsense. If Remote can't reach what it is trying to point at, it doesn't show you anything at all.
So far, iTunes Match is a massive win. I'll update this as I encounter different aspects of it.
ETA: I've been ripping discs all day, and iTunes Match seems to (mostly) keep up. It can get ten minutes or so behind at times, but it's pretty fast.
ETA still more August 8: The project continues (altho the end is now in sight!). I continue to have 100% matching [ETAYA: turns out I was wrong here and am still investigating what's going on. I misunderstood the display and didn't have one of the columns turned on; more is uploading than I realized], so I don't know what people are talking about in all those reviews about a fifth or more of their music not matching. I will note that historically, I ripped at lossless (so going to iTunes Match is actually a slight decrease in quality, but I'm okay with that), and for the rip-everything-I-own project, I'm using 256 (which is exactly what Match uses). While I have ripped some of my husband's CDs (in the past, and, most recently, I realized that while I owned Graceland on tape, I apparently did not buy it on CD and that just seemed insane. He had it handy, so I ripped his rather than buy it again. I feel like this has to be okay.), I have never put music into my digital library that came from music services, and I'd be hard pressed to identify stuff I got from anyone other than my husband (ripping of non-owned CDs, that is). I did have a few non-commercial CDs (friends gave me copies of stuff they owned), which I trashed without copying. iTunes Match really isn't just about legitimizing piracy; it really is about separating from the plastic.
I did have a lot of network errors yesterday, that caused a lot of stuff to not upload to the cloud. :( I ultimately shut everything down, restarted my computer, and tried again. Same problem. I was getting worried, but I tried again today (without more restarting, and it worked fine). However, I am now noticing that while the mobile devices window onto my cloud catalog were keeping up the first day, they are not currently keeping up and I'm not sure how to force an update (that is, stuff that I _know_ is in the cloud is not in the cloud listing on my phone, type of thing).
I think I still trust this enough to continue. Worst case scenario, at least my entire library of CDs is in iTunes _on a portable hard drive_, which is Not Nothing.
There are more limits on iTunes, iTunes Match, etc. than I had realized. Specifically, there's a 5 computers for one iTunes account limit, and 10 devices for one iTunes account limit. I'm not worried about the computer limit, but the device limit has me worried, since all the mobile devices except for R.'s phone are all on my account. However, they don't all have cloud/match setup, so I mostly have to worry about the implications for accessing video purchased on the account.
I think that when the kids start to outgrown "kiddie" stuff, and develop their own distinctive tastes, I'll have to set them up with their own Apple Store accounts, to prevent this from becoming a bigger problem when they are older and we have still more devices, and also to handle their ultimate transition to Hey Mom I Don't Want You to Know What I Buy with My Own Money, which, if I recall correctly, I was not technically allowed to feel as a child, but I still acted upon starting around age 11 or 12.
Which is not very far off now.
ETA Still more: Well, I didn't figure out how to force a refresh on the mobile device side, however, they are working better now. I took a look at the 10 devices listed on my account page at the iTunes Store and realized that there were Problems. We only have the one iPod Touch, but we had to replace an old one, and the old one never was removed from the device list. There were some other problems with an old iPad as well. I may have been over the 10 device limit, and that was causing some problems. By removing known-gone devices, perhaps the problem fixed itself. Or maybe just enough time went by. *shrug* As with de-duping, cleaning things up probably isn't _bad_ per se.