Review by VG247, which is very positive:
And Polygon’s Charlie Hall really likes the co-op:
Personally, I’ve been playing since the pre-order beta started and I absolutely love the co-op. I guess it’s the game I never knew I wanted, since historically I’ve been shunning more “realistic” hardcore shooters while leaning more towards arcadey shooters like CoD and BF. But for me, this game beats them hands down. The intensity of Insurgency combined with the pressure when being one of the few still alive is riveting. Also, it helps that the gunplay is great and the awesome soundscape is maybe only surpassed by the already mentioned Battlefield series.