Although we've only seen this so far on the editorial Nokia E7, it's likely to also appear for the N8, C7 and X7. Compatibility with the E6 isn't guaranteed (screen size), but who knows....? Comments welcome if you're seeing this fresh new version of Nokia Music on other devices.
All our previous Symbian^3-class phones are/were still showing the old Web-based version of Nokia Music, so this standalone client is something rather fresh and welcome.
The content is the same, though, a typical modern music store, serving up DRM-free MP3 at 256kbps - you'll need to sign in with your Nokia account, of course, in order to buy music.
A restart of your phone is needed after installation and this is because Nokia Music installs at quite a low level, it's a system component and effectively replaces the old version in the firmware image. As a result, it's also not listed in Settings/Installations, so can't be easily uninstalled. Not that you'd want to, but worth mentioning, in case you're tempted to install an SIS for another device - wait for it to appear officially!
Comments welcome - I'd love more data points here. Also comments on attributes of the music files served up, should you fancy a little (ahem) Rod Stewart...