I am tired of people writing comments like this, "Not Fincher's best". Honestly who cares. We all agree that Fincher's best is either Seven or Fight Club, two outstanding masterpieces. There is a big margin between a film like one of those and a terrible film, and people don't seem to realize that. These people even do this with other filmmakers like Spielberg or Scorsese, the fact that these filmmakers don't reproduce Schindler's List or Raging Bull doesn't mean that their new stuff isn't good, or worth seeing. I think it is a stupid way to comment on a film, eliminating the critic's credibility. I was lucky enough to catch an advanced screening of Zodiac last night, and I must say that at first I was discouraged by two things, some of the comments I have read and the running time. However I am glad to say that I enjoyed this film, very much. It is a solid suspense thriller that pins you to your seat. Being a true story adds quite a lot to the experience, and besides, Fincher did a wonderful job is staying loyal to the story and at the same time adding his unique flavor to it. The cinematography, like every Fincher film, is great, the darkness and griddiness of the story are perfectly portrayed in the film's visual elements. I was surprised by the picture quality of the Viper, the digital camera with which this film was shot. Many people have been criticizing this choice, but I respect it, he is embracing a new technology and making it work. Of course its still not a match to 35 mm, but if quality filmmakers don't start experimenting with it, it will never be. Now the reason why this film falls behind Seven and Fight Club, I think, is because of a problem with the characters. They seem to be a little weak at times. The performances were great, especially Robert Downey Jr., but I think that this film falls short, when it comes to a true exploration of complex characters, which is the key to Fincher's previous films.
So... my advice to everyone is to ignore most of the negative comments and see the film yourself. I found it to be a great story told in a remarkable way, very entertaining, with great performances, and wonderful direction.