Super fun when it works. Mercs are first-person and you can set controls to same as COD. More like hide-and-seek than run-and-gun but it's unique. Teamwork is more crucial.
But there are freezing problems online and the connectivity is lacking so it can be hard to get in a match. If they patch the matchmaking there are enough players online at a time but right now it's like everyone has strict NAT (similar to Assassin's Creed 3).
Ghosts will have much larger player counts so it's mainly a choice between more players or unique multiplayer modes.