Beat it last night, but still have co-op to go through.
My biggest complaint is the loading issues. I feel if this was any other game Gaf would be all over its nuts and deem it inexcusable. Not sure why Valve isn't getting some serious flak for this. Loading screens are numerous, lengthy, and plenty take you right out of the experience. Some sections of the game are literally 10 seconds of you just following a straight path laid out before you "chase scene", and then it cuts off any suspense that can build up with a loading screen right in the middle of it to load up the next section.
I felt the game was also very easy. Almost too easy. When they were first showing it off I was excited to see that it might finally have some super complex puzzles, but I worked through everything in minutes without issues of any kind. When a game is this short and this easy it can really take away from what's good within the package. Another thing I found odd was the puzzles as you went didn't necessarily get harder, once you got through the main gel puzzles the game seemed to give up entirely on challenging you and it'd throw in rooms that were literally 30 seconds to solve in ease. I wish the game could have maintained its momentum and kept building up to the ending.
The rest of the game was superb though. Gameplay, soundtrack, design, voice acting, story, and one of the best endings to a game in a good long while. The PS3/PC connection ideas are genius though---that deserves the most praise and I hope more developers start to follow suit with this idea in the future.
Now if my buddy would get online so we can do more co-op I could maybe find that the more challenging things are within the co-op perhaps, but I doubt it. Good game, but the hype train is a little too much for what you actually get.