Wouldn't mind an option to allow the game to remain unpaused as focus is lost.
By using -popupwindow and window mode, I have a borderless version of the game.

It's really nice to see the visualiser return in the game, but it would be very usefull to allow workshop skins to define themselves as a visual mode (or freemode) instead of a competitive one, allowing the music to continue as the user interacts with other windows.

The first game had a similar aspect, where alt-tabbing in freemode just allowed the game to continue, autoplaying the next song.
http://www.audio-surf.com/forum/index.php?topic=2789.0
I would really like this to return for mods