There is so much going on here that I was captivated by what I saw. The LA-is-corrupt-and-so-are-the-cops plot is too convoluted to explain. Here is one review that I liked. I also recommend reading Roger Ebert's review.
This movie is a well done period piece that presents itself as modern film noir and has an all star cast. With all that going for it, the film naturally has an attitude about itself: This movie wants you to believe that it is great film. In some ways it is, but most of the movie is dialog, sometimes corny, punctuated by frequent moments of extreme violence. There are a large number of speaking parts, and a high body count. The action scenes are certainly intense. There is a gritty realism to the movie. When it was over, I was thinking that the movie is good, and technically excellent, but I wasn't sure if it was great. My problem is that I don't totally believe it. Parts of the movie are based on real events, but the story as a whole is a little too far out there. This is not good for a movie that is supposedly a period piece about 1950's Los Angeles. Now if I could just think of the movie in the same way as "Pulp Fiction" then I would feel differently about it, but I don't think that "Pulp Fiction" was trying to be a realistic period piece. Maybe that is the point; the movie is not trying to be realistic, but a more modern and intense version of classic film noir.
In places this movie is pretty gory.. This is not the kind of movie that I would want to watch over and over.