This game had a good start, but it turned out to be a big disappointment for me. At first, there's a nice new location - swamps - and lots of changes for the better compared to the original Stalker: weapons have to be upgraded in order to be effective, so you're motivated to earn money; artifacts are rarer, more valuable and much harder to find; anomalies are invisible, you gotta throw screws around to detect them (just like in the book)... Nice.
First thing I didn't like was that the game was always pushing me into some action. Your faction constantly gives you orders to conquer this or defend that and usually you don't even have time to do everything they want, let alone to just wander through the location or go treasure hunting. Shadow of Chernobyl was like experienced stalker guiding you in the strange world of Zone, while Clear Sky is agitated drill instructor on the training ground yelling at you: "GO GO GO!"
There aren't many new locations: Swamps, Red Forest, Limansk and Hospital (which is not really a location, but just a one long corridor). Old locations changed only a little, so overall there's not much of a new content. I didn't mind though, I was happy to play improved Stalker in new clothes. Then I arrived to Limansk and the game suddenly changed into Medal of Honor: Chernobyl. From there on you play linear shooter, the rest of a game is basically a "tunnel" from Limansk to the power plant, full of enemies. And you can't go back and buy better weapons or armor. Drill instructor has definitely taken over the show: "Say goodbye to the the open-world gameplay, you f***ng hippie stalker, and GO GO GO YOU MAGGOT, you're in the army now!" So you're obediently trotting onwards as game throws enemies in your path, you're lowering the difficulty as your medpacks slowly vanish and hope that you won't run out of bandages and ammo and that the game ends soon. And when it does, you're rewarded with short lousy outro (however, the biggest reward for me was that the game is finally over).
So there you have it. Clear Sky doesn't have much new content, it's unbalanced and the second part is downright frustrating. I wonder why the game creators switched genre so drastically in half - I don't think it was an intention, maybe they were simply in rush to finish the game.