21 Grams: What is the weight of forgiveness?

Just saw 21 Grams. Went with two friends. The movie ran 2 hours, plus.
When it was over, the friend on my left said “That was two hours wasted.” The friend on my right said, “Wow, what an amazing spiritual movie.”
We all agreed that the acting was extraordinary: Benicio del Toro, Naomi Watts, Sean Penn and the previously unknown to me Melissa Leo.
Alejandro Gonzalez Inarritu, the director, made an earlier film, Amores perros(Love’s a Bitch) that I thought was great. This film had some wonderful moments, and was beautifully shot on what looked like digital video, but there were some major character inconsistencies and plot bloopers that suspended disbelief. For example, Sean Penn plays a math professor, but he never works, and his affect is way closer to tough guy than academic. As his English wife, Charlotte Gainsborough is beautiful, but her motivations seem hard to understand. Only Benecio del Toro and Melissa Leo(playing his wife) pull off completely coherent characters.
The last word: Definitely worth seeing, amazing performances, but the script writer should have made it hang together a little better.