Surprisingly good for a multiplayer game. The gameplay is fund, the waiting to playing ratio is moderate and no annoying "you don't want to wait? Why don't you spend 2$?" or "Other players are stronger than you? Why don't you spend 5$ on an item wich is five times better than anything freely obtainable?". A 5/5 from me (which I rarely give to multiplayer games).
Thanks to everyone who commented. The problem with the sound is partially a bug on the side of the unity engine. To avoid this I'd have to change the way i implemented playing sound individually at every point I want sound to play. As a hot fix, I removed the non working part in order to avoid confusion. The m key for muting the musik alone still works.
Very good game. I like how you brought the inverse td levels out of the bonus into the main story. Also it is very convenient, that the upgrades can be placed freely. A clean 5/5 from me.