Groove is working fine on my upgraded SP2, but this version is limited -no Playlists nor Now Playing on the menu. I'd say still limited, but I saw Now Playing in a video of an earlier ( I presume) build? or version. Music|Mode screenshots look good/promising with hints of Zune, but not really. I hope to see a video showing it off soon. Also, reading the website, including the very helpful developer's blog, it sounds even less-ready, operationally, than Groove.
It's still SO early, though, for all things W10. Whatever I use will have to work well with my Groove Music Pass, my soon-to-be W10 phone, and ideally (in my dreams) my Zune players.

Meanwhile, I'm having fun learning, and look forward to great new devices.