I just read a recent interview with some very good news. We know that co-op is in GRAW, but 16 player online co-op is also confirmed, and you can play with 4 player split screen as part of that larger 16 player co-op game. This is great I'm the only one with a 360, yet my friends and I are all serious co-op buffs. I'll be buying more wirelss controllers in preparation for the game's release.
You can you play co-op modes on all the multiplayer maps, complete with in depth options to make even more interesting situations than the standard kill all enemies on map. One example from the interview:
if you want a big challenge in Co-Op, set up a five-zone Co-Op Territory mode, with around 10 players. This means you have to split up into teams to each defend the five different zones, as the AI enemies storm and try to capture them. There are a lot more options; you could basically play a different combination every day for the next couple of years.
Unfortunately, you cannot play through the single player campaign in co-op, the scripting just couldn't support it. However, there is also a second campaign just for co-op play set in Nicaragua.
So unless they really bork the basic gameplay, the feature set of GRAW is looking great. Ghost Recon 2 for the xbox was fun to play, if a bit clunky in framerate, but the vidoes I've seen of the GRAW gameplay look smooth. So this'll be a day 1 purchase for me. The co-op alone sold this game for me and playing 4 players on a widescreen HDTV is going to be very fun.