You know, I'm really not feeling this. I used to defend Insomniac's decision to make co-op separate from the campaign, but at that time I was under the impression that the co-op campaign would be just that, another campaign. The way it works now, it seems like a mix of GRAW style co-op, and Unreal Tournament Invasion mode. And making creatures bullet sponges, I don't see much sense in that. I guess it will be cooler once you get to the real bosses, but the Titan is pretty terrible.
I need to try out some more of the MP, the Core control mode in particular.