Although certain people would have you believe that 21 Grams involves intricate, interleaving plot lines coming together to form a carefully planned story, it doesn’t. After seeing it, you might agree with them, you’d be wrong.
The real intelligence behind the film is the editing. The whole thing has been cut to give a fairly bland story a sense of interest by showing what happens to various characters out of order. This has been done far more convincingly elsewhere (Memento, for example), with more imaginative reasoning behind it.
Despite this reliance on editing, 21 Grams is an ok film, but certainly not uplifting.