Innovative take on the TD genre! Addictive in co-op w/friends. Quick to learn but surprising depth if you commit to it.
Having a group conversation via Skype is highly recommended, since this makes it easier to plan the layout in the building phases as well as coordinate the action!
Pretty stable. Sometimes it may take a few tries to join a multiplayer game, though. But be patient; it will work after a few tries. A game can be joined even during play, but only in the planning phases. So: Use Skype to coordinate play with friends.
A good innovation on the tower defense genre. I really hope there will be more games like this in the future. The developer has promised new content added automatically through Steam. A couple of new maps has been added already.