I'm honestly not surprised at Apple, I never thought they would ever do it. Metro is Microsoft's mobile environment and Apple/iTunes doesn't support any mobile environment except their own. Thus no Metro iTunes ever.
Right now on my Surface Pro, what I'm doing is I use iTunes on the desktop to manage my library and have it all downloaded to my SD card which is setup as a Virtual Hard drive so Windows can index it. It works and I can use the XBox Music app for playback which is not so bad since the last update.
I also get a lot of downloads to new music from labels, marketing companies, etc, so I add it into iTunes, which copies it to the SD card and pushes it to iTunes Match at the same time. I also occasionally run
Amazon's music importer to push the new tracks there too, which makes them available on my Android phone.
Apart from a few third party Google Music Metro apps there really is no true* cloud music app for Metro is there? iTunes Match is about the only reason I use iTunes anymore. At about 120GB of music, I always hated backing it up and maintaining it. Also the iTunes music store still has lots of exclusive content (like live performances) that's only just starting to be matched by
Amazon.
*True cloud music support being one that supports uploading your own collection in addition to match.