Well, it's safe to say that this is definitely a David Lynch film, from that point on, if anyone has seen any other his other pieces, such as 'Blue Velvet', be prepared for a strange ride.
Mullholland Drive, in a nutshell, is a mind-fuck to a certain to degree, as it consistently manipulates you into a false sense of direction, allowing you to judge just what type of film it is, then suddenly, completly shifting the genre, as well the narrative of the story.
An example of this, is the constant character swaps, which appear at first to be completly unrelated, then begin to merge into one story. At this 'apparent' merging of the characters stories occurs, they suddenly explode and fragmentate into different directions, as well as presepctives, acting almost like a labyrinth in that sense.
The film includes numerous elements of genre's that would otherwise not fit the intial 'criteria' of the first
few scenes, for example such elements as psychology, porn, crime, horror, dreams, hollywood, all appear within this film.
Mullholland Drive, in this sense, merges these different themes, and completly 'disobeys' there genrics, almost making the statement that 'why should films be so genric and linear', and using this theme to portray the inner pshyique of an indivduals mind, who uses these elements to overcome issuses in her life.
As much as I found this film 'weird' on a number of levels, it definitely is a must see, and perhaps after reaching the end, another watch is needed to get the most out of the film. In relation to post-modernism however, this film seems to portray how 'undecided' the subject is, and undefined :)