Space Marine Free "Exterminatus" DLC is Waves of Ork-Destroying Goodness

Had a brief opportunity to play the new Space Marine DLC last night, it's pretty awesome, the addition of co-op is perfect. Basically massacring waves of orks, they get progressively harder as you progress through the waves. My only gripes thusfar are:

1. No way to pause, you literally have to keep going or die, get the catheter ready!
2. There doesn't seem to be a way to progress through the armor challenges to unlock new armor parts in co-op.

But on the plus side, the leveling happens a lot faster in co-op. I just unlocked the plasma pistol last night :)