The plot is good, not jaw dropping in terms of surprises but it still excels in its presentation. The main characters are great and the side characters get their moments as well, although they pale in comparison (but they are side characters so that is ok). On the other hand they even get a tiny bit of character development and there even was a moment that reminded me of the movie 28 weeks later (I wonder if some of you know what I mean).
As for gameplay, there are enough mechanics to keep it interesting and some of the conflicts even have the potential of multiple ways of solving them. However, most of the time you will be guided through the levels and there is usually just one way. The riddles are on the easy end of the spectrum. They do break up the pace of the game though, so it is welcome. The sounds are didn't really catch my attention so that usually means the sound guys did their job well. The music composition is overall great and carries a a lot of the overall tension. Which came apparent when during a chase scene, it bugged and was gone, just to come back, to go and so on. Generally the game runs well though. The graphics are good, the levels well designed.

If you want to choose between going to the cinema or buying this game - buy the game. It is definitely worth it.

PS: Replayability - I don't think so.