I have now watched the rest of 'Biutiful'.
I think that David did a good summary of the film.
The film does well, to transform Badem from an individual involved in illegal activities, to someone you do care about by the end of the film. The film also makes you care about the fate of his children, and to a lesser extent his wife/ex-wife, but it is inevitably ambiguous how the future does turn out for them.
Regarding the opening/closing sections, I interpreted the opening section as Badem playing with his grown up son, and the closing section as Badems dead father coming to collect his soul. Was my interpretation correct, or have I missed something?