Yeah, I'm kinda curious how iTunes Match works myself. If you have a song that you ripped from CD but in the iTunes store and / or a DRM song purchased from iTunes, it don't think it changes the song locally on your computer. But if you download it onto another device from iCloud, you essentially have a different version that what's stored on your computer. So the next time you sync that device, does it OVERWRITE the previous version on your computer? If so, what happens to your metadata (lyrics, cover art)?
Tony