I don't understand public reactions to this game. Case Zero was the hottest selling XBLA game in months, with the highest sales for any XBLA game in that timeframe, and yet I am the only one on my friends list of 25 or so people playing the full game.
This game is awesome, I have played it for longer periods of time than any game in awhile. Co-op is a blast, combining weapons is satisfying, and time management is actually pretty challenging (but not impossible by any means). Planning ahead is not something I thought I would do in a zombie video game, but thinking about if I were really in a similar situation, it makes absolute sense and works perfectly with the concept. I'd better not go check on the hostages in the Italian kitchen without bringing a homemade lightsaber and some juice mixes, for instance - never know what's gonna happen.
Managing your party once they've joined you is really simple, and handing them a good weapon makes things LOADS easier. I've even handled boss fights with a couple of stragglers armed to the teeth, and it was certainly not the bad idea it would have been in the first game. There are lots of little things in the game (modding dirt bikes, finding new rides, all the clothes and shit, blending drinks, etc.) that you don't NEED to do, but once you decide to try them out, you wonder "why haven't I been doing this all game?"
The only major caveat I have with it is that co-op saving is kinda shitty. You can load your character from a save you have and help them out in their campaign, but rather than just saving the leveling you've done to your character, the save you create is actually a save of THEIR game. So if you load from Day 3 with a level 30 character, and help someone out on Day One, your save will be of a level 30 character on Day One. Oh well. Doesn't wholly negate the fun I've had with online co-op. (And how has nobody mentioned that yet, but plenty have brought up the afterthought multiplayer that exists solely as an online bank?)