Agreed, worth allowing the iTunes Match pass to complete prior to sorting a view on the iCloud Status field. A helpful supplement which is more reliable for tracking is to create a Smart Playlist using the iCloud Status as a key criteria - creating a few playlists for 'Matched' and 'Uploaded' gives a great idea of progress.
I did some checking. Looks like the Apple-TV (Gen 2) is just storing it's configuration information and playlist data from the iCloud between power-on-off cycles (I physically unplugged the unit to test this). It buffers down the current song, and seems to at least buffer the first few seconds of the "next" song on the list (even in shuffle mode since it knows what the next song is already). This latter logic seems to help speed the transition from the current song after it ends to the next song, a nice touch of programming there Apple!
I tested, at the point while the current song is playing, one can disconnect the ethernet cable and the song continues to play (granted that it had to have been streamed in completely), so it appears that it's trying to buffer in all the song as fast as the network will allow. In this scenario, the next song failed to play. This tells me that the next song is not buffered in, nor are songs being "saved" on anything more than a temporary basis.
By the way, checked, and in no Apple documentation does it say to restrict any changes while iTunes Match is occuring. Yes I agree it's a "good idea" not to mess around with the Music Library while iTunes Match is going on - but Apple should document any restrictions and/or inconsistent behavior such as the sorting not working exactly as it should while iTunes Matching - it also doesn't gray out my ability to manipulate the Music Library. This is a just another example where Apple's mentality of not telling a user exactly what is going on seems to be lacking good design practices, IMHO.
I agree there is a lot that Apple could document with respect to iCloud that it has not of yet and in fact some of its statements to date are a tad contradictory (I know, that's like being a little bit pregnant).
When I offer advice, I try to take into account user experiences, as well as what Apple has documented. For instance, looking at various user issues, it's pretty clear that while Apple says you can continue to do other things in iTunes while Match is processing, people who have decided to do much more than play music locally (change metadata is one example) have had problems. Or, if you look closely at Apple's step-by-step process for getting Match going, while it does put enabling iTunes Match on other devices after running iTunes Match on the first device, it really doesn't explicitly tell you that doing otherwise can result in unexpected behavior. The board is full of people complaining that they see "grayed out" songs they can't play (the database is there, the files haven't been uploaded, but they don't know that).
I expect Apple's listing of support docs will expand over time. Meanwhile, it's pretty much up to us.
In that regard, I put together some commone issues and posted it to this thread this morning. You might find interesting.