Probably the smartest decision from microsoft. They made it free so no one will pirate it and they charges for DLC so that the game can still be profitable. I think thats a learning from social free to play games.
I love call of duty(though love Bad company even more)... but already there are too much call of duties to take. Advanced or future call of duty is okay to freshen things up ...but space?seriously? whats wrong with zombie warfare..:P