This could be the first Insomniac game since PS2 that I don't buy, that being said I'm not really into co-op and I think this game could be fun playing with friends as it seems designed from the ground up to take advantage of that and we know from R2 that they have some good experience in this area, with a 'generic' looking game like this a lot will rely on the feeling of the weapons and how the characters control in the environment for me, take gears for example, I actually find the franchise past the original fairly generic but they feel so good to play, very tight controls and good feeling weapons go a long way, and also good AI of course, so I'll be waiting for a demo/hands-on before I rule the game out completely.
If anyone from Insomniac is listening please make sure this weapons 'feel' good, so many games forget how important that is, simple things like good recoil with the combination of well timed strong vibration feed back for example makes a weapon feel weighty and fun to use, also give some weight to the weapons through the audio, it helps the player feel empowered and keeps those endorphins flowing.