Just played through it. I wouldn't say that Kane & Lynch is bad by any means, but I feel a lot of the complaints are justified. The AI is abysmal, especially in the Cuba levels... my men kept dying because they decided to take cover in the line of fire. My game also froze a few times, and it was often in horrible spots. By that, I mean after the spots that had taken several tries to beat.
That being said, I feel it's an underrated game. I love the story, it's always nice to see a darker story in games. The dialog is brash, but let's be honest... is a group of mercs going to be speaking properly in the line of fire? I also kind of liked the loose shooting in the game. No, the guns weren't laser beam, MW2 accurate, and often times it takes a lot of ammo to bring someone down at range, but I honestly felt that it fits in with the whole premise of the story being one botched plan after another. The revive system is pretty cool, too. I liked the balance of it... adrenaline can save you, but if you abuse it, you overdose. Overall, I'd say it's a pretty good bargain for $11 or whatever Gamestop or Amazon charge for it now, it's got a pretty fun single player mode and a multiplayer mode that I hear is quite fun (I never got around to playing Fragile Alliance, but it sounds very interesting).