I've subscribed. Been waiting for this for ages. Its the reason i went for a 16GB 4S rather than higher capacity. Especially now you have the ability to delete albums from your devices as well.
Setup my matched service overnight. Only 1600 of my tracks couldnt be matched (compilations etc) and have now been uploaded into the Cloud as well.
Been testing it this morning, works faultlessly. Download an album from my library in a minute or so at very good quality. Finished with it, gets deleted, can download another or just queue a few albums to download. You also have access to your custom playlists from your iTunes library, and can choose to download all tracks in a PL.
I think its a superb system.
My only gripe, and its a small one, is having to go into settings to turn off the option to see all music in the cloud. There should be a toggle from within the music application to show all music, or just music downloaded on to the device. The ohter small problem is that i can see ALL album artwork from my entire matched Cloud library, even though i have only downloaded 1 album on to my device.