I quite liked it. I've played it for both PS3 and PC, and yes, cheating is inevitable, but that shouldn't ruin an epic game. Personally, I think singleplayer should be able to stand up on its own without multiplayer, multiplayer being the nice addon, not the other way around. So I won't talk about the multiplayer.
Very short, almost Halo short. I have realised that Infinity Ward hate the player.
But I very much enjoyed the finite amount of enemies. Call of Duty 4 failed in that respect, where the inevitable camping and occasionally shooting was not an option, where your position would be flooded with enemies and grenades almost instantaneously. Leaning is now gone for the PC (non existant ever on the console) which can lead to getting shot quite easily when trying to take a few pot shots at a group a bit further up.
The additions and removals of certain weapons I very much liked in comparison to COD 4. For example the addition of the Javelin, Stinger and AT4 as opposed to the classic RPG-7 which could go anywhere, really help taking out enemy helicopters. I enjoyed in the Campaign using the Predator Missile for the sole reason that watching little red squares dissapear on a black and white screen is quite amusing. That being said, I like tetris for the same reason.
I much enjoyed the thermal optics and the ability to customize your weapon further, and without it becoming a Crysis: Warhead style weapon where you can equip silencer, extended magazines, optical scope, laser sight and cola vending machine on the weapon as long as you have seen somebody else use it. I didn't like the riot shield for the reason that the enemy has it and can shoot, I can not. However it did prove very useful.
The only part of the campaign that I thought really let down the realism they were supposed to show were the two missions where you get to ride around in a snowmobile and boat. This boat was made out of plastic. Pretty much like an air boat. I remember being shot at. Why didn't the boat pop, and on that note why didnt the enemy boats pop when I shot them?
Ah yes finally the story. I very much like the story of it, leading off from being the faceless Soap McTavish the FNG or Private Paul Jackson, to now Gary 'Roach' Sanderson (RIP) or Private Joseph Allen (RIP) or James Ramirez. The plot twists and the return of my favourite character Gaz as the similar sounding Simon 'Ghost' Riley. They were indeed similar. They both have a coincedental tendency to get shot with a high-caliber pistol on Day 6.
So thats my take on the new call of duty. Hope I didn't strain your eyes reading, I just thought I'd go through anything that came to mind