From the Movie Snob:

21 Grams. (B-) An overripe melodrama with a twist: the director filmed a story about three strangers brought together by a single tragic event, chopped 2 hours of film into scenes of 1 to 3 minutes each, and then completely rearranged them. Thus, in one scene Sean Penn's character is walking around perfectly fine, in the next he's in a hospital bed stuck full of tubes, and in the next he's staggering weakly around his house hooked up to an oxygen tank. The other two strangers are Naomi Watts, playing a happily married mother of two little girls, and Benicio del Toro as an ex-convict who has found Jesus and uses Him to subdue his darker impulses. To say more would be unfair to the viewer; suffice to say that I did not find this movie nearly as satisfying as many critics seemed to, and I found it difficult to tell whether Watts and del Toro really gave Oscar-caliber performances because the lack of chronology keeps you from growing along with the characters.