Something weird about Windows RT/Modern-style Windows apps: My Microsoft account exposes a certain amount of music that managed to be saved in the standard C:\users\username\music Library from whichever machine I accidentally saved music into that folder from. So that music shows up if I sign in to a Windows 2012 Server and my non-Pro Surface with the same account. Neat. It specifically doesn't grab music from any other folder configured as part of my Music library on any other Windows 8 machine. That seems highly inconsistent, something I should have granular control over and as far as I can tell that control is NOWHERE.
The standard Music app for Windows 8, the one that's just called "Music", displays releases from itunes and from Amazon, but doesn't provide any hooks to connect to an existing itunes (ew) or Amazon account. There's also no native support for Google Music, no native Pandora and no native Spotify, though there are at least a few apps that can talk to those services at least well enough to stream data.
The thing is, this seems to be an aggressively poor feature set. Show us Amazon, but don't talk to Amazon. Magically import SOME music, but don't give the user any control over what got magically imported.
I also notice that OneDrive doesn't support symbolic links. I can add something to my Google Drive by using mklink so that for example I'm not duplicating content in C:\users\username\Google Drive\ that already exists elsewhere, but Onedrive doesn't follow the link to actually copy the data, resulting in something that amounts to a broken shortcut on any other machine. I've been messing with scripts to duplicate some Google Drive and OneDrive content, but if I have to maintain the same set of data twice, it's just not worth dealing with it.