A friend and I saw Babel last night, and I loved both Gustavo's and Rodrigo's work! It is well worth seeing, and I'll be getting the soundtrack soon.
The sound in the theatre was too loud, so that was annoying. Nevertheless, Gustavo's plaintive guitar strains - Spanish style for the scenes in Mexico, and Middle Eastern for Morocco - were completely identifiable as HIS. His use of simplicity and silence - no Brokie could mistake it for anyone else. There were also more frenetic, very intricate pieces for more dramatic moments to build tension - charango, I think - which were amazing.
And Rodrigo - goodness - the sweeping vistas of the deserts, infinite blue sky, relentless heat, Tokyo - unending city at night - the sense of lights as far as you can see, the fast pace of Tokyo city streets - unending motion, some terrific aerial shots. There was also excellent work of faces, expressions up close and personal.
(I'm no critic, so someone please come along behind me and do a better job describing this!)