Bad, not very bad, but bad nonetheless.
The Campaign made feel totally detached, I didn't even know the important character's names till the end.
And the attempts to make me feel sad the way CoD4 did, fell flat on their faces.
As for online, I have rarely seen a more busted game, and never out of a major developer.
The new guys get the worst guns and all the cool items abilities and gadgets are at the back end of the leveling system.
The maps glitch easily enough that it's possible to get shot ANYWHERE on the map and not know where it came from.
Artillery strikes are useless, you have no control over what actually gets hit,they aren't like Cod4's where you could bomb a 20foot square to hell, and it was mostly right where you put it.They spray all over the map, and kill nobody.
Dogs are impossible to fight, since they take three shots to kill and 1 bite to get you(hardcore)
The weapons, while realistic, are garbage, they look like playskool toys and the majority don't have a defining ability.
Let me explain this point, in CoD4, the G3 was for the demi-sniper spy, the M4 for the less experienced versions of such, they were neither of them powerful, but the had accuracy out the Wazoo, and they could kill 2 or 3 people without a reload anyway.
The Automatics varied from high power low accuracy(Aka, Ak-47, M60) to the Bullet Hoses(P90, uzi)
They balanced each other, a G3 was crap at pointblank, and a p90 couldn't hit the broad side of a barn at 10 paces. You chose your style and worked to it's advantages.
In WaW, you have Bolt action(medium power, slow fire rate, reasonable accuracy) and rifles(less power more fire rate), shot guns(universally known for no range, an heaps of power), MG's(mostly low accuracy, high power high fire rate).
That;s okay, except that the good guns in each section(Fg42,Stg-44, PPsh-40)
were all acquired PAST lvl 40, so the first 40 levels are entirely an exercise in frustration as you get repeatedly ass-boned by a guy with an power gun, simply because he bought the game before you and has them now.
I suppose there is a case for them just being harder to use, but that would mean that people would do like in Cod4 and use them because of a preference, I have not yet seen a high level player using anything other than the power guns, excepting the challenge completion.
Bouncing Betties are invisible, unlike Claymores, which means that you cannot hope to move across the map in peace, because either a sniper will get you while you look for mines, or you hit a mine running from a sniper.
Last Stand(Second Chance) and Martyrdom are back, damn Treyarch to hell for that.
And finally, the game just has issues, people get locked out of games, booted from THEIR matches, and random skips in the game cause people to resurrect or simply take a whole clip without dying.