If I'm sitting on the Online screen, it would be nice if a sound played when an active VS game changes from Waiting to Play. I'm tabbed out while all the matches are waiting, and I know from previous async multiplayer games I don't like having too many games going at once. So I'd rather just get notified when a game is ready.
Viewing post in Feedback from First Access
Yea - from here.
http://i.imgur.com/b2kP3Ma.jpg
Or to be honest, any time the game is open that the player is not already in a different online game. e.g. skirmishing while waiting for the opponent to make their move.