I don't think it's free , below $20 is mentioned in this article from their website . I know free is below $20 but I still think they'll charge for it.
well ,just had a quick 30min play ( not many playing on the servers ) but overall it seems alright especially as there are bazoookas and you can shoot buildings down brick by brick to get at the people inside, the mouse set up is extremely fast thou , but yes it looks quite fun if there are enough players and the maps were quite smallish.