Apparently different versions exist. This IMDb site lists the running time as a little over two hours, but the version I saw was listed at well over three hours. It was very long, basically two movies back to back. Many of the scenes were shown twice, from the perspective of the two principals, with differences that were sometimes striking and sometimes very subtle. I found it fascinating, but I can imagine that some viewers will become impatient. (My bladder did -- don't go into this one with a large Coke.) I would like to see it again on video so I can go back and forth and compare versions of events, but I am worried that I'll end up renting a shorter version. The existence of different versions makes it a moving target -- it's difficult to review, and even more difficult for a prospective viewer to evaluate on the basis of published reviews, if you don't know which version the reviewer saw. They say the difference between a good haircut and a bad haircut is three days. Well, the difference between a good movie and a bad movie may be as little as three minutes, edited out or left in.
I'm giving this movie 9 stars because of a single line of dialog that blew me away and changed my perception of a lot of experiences in my own life. You can't ask for more than that from a movie. It's a comment made by one of the minor characters (the waitress) -- almost a throwaway line, really -- about the effect that people have on each other in relationships. I don't even know if it is included in the shorter version of the movie.