Airlines insisted on having reversers available. Fernando_Covas has the info correct on why the outboard mills don't have them.
Come on now - give big bird a chance. Let's see what happens when she enters revenue service.
It will be interesting to see the real numbers and the relationship to the Boeing VS Airbus
PR spin on economics. Boeing states that the re-engined and stretched 748 will be cheaper to operate per seat mile than the A380.