The passing DLC campaign is short, but the amount of detail in some sections is pretty high. I was expecting a more intense campaign, like Parish, but it's a pretty soft level unless your playing verses with it's environment more suited for ambushes than any other level.
The Realism Mutation is absolutely brutal. It's more than possible to waste groups a bare 50 meters away from the last Safe room.
I have found enough like minded players to have some fairly regular games of high quality. Even then, random people who join tend to hold themselves up to a pretty high standard with the number of arses much lower than expected (achievement whores, 13yr sailors, arsebergers). I guess the extra investment in hardware draw a higher denominator crowd than the 360. Still has it's fair share of rage quitters.
Still wait on the Mac port, April is a bout to run out.