I saw this thread and had to respond - Memento is my all-time favourite movie.
This movie uses 'form and format' as much as characterization and plot to further your experience. It is through this format that the viewer is forced to recall past scenes and reconcile it with what is happening now. The truly interesting part is that sometimes you are 'adding' what is happening now to a past scene, recalling where that scene ended. OTHER times you are 'subtracting', recalling where a previous scene BEGAN, and trying to see how the current one will enable it. This experience is a little mesmerizing, and to some degree, helps you experience the condition (short-term memory issues) of the protagonist.
I'd give this a 10 out of 10!! Guy Pearce is fantastic. If you liked this, seek out 'Following', where Chris Nolan 'cut his teeth' on this style of moviemaking. I thought it too was great, though less neatly composed, and with less engaging leads. I envy anyone seeing this for the first time. I believe it was independent, also, which is a nice dig at the big budget films!
If you liked Nolan's Batman, you have this film to thank.