I'd be interested to know the "curve" drawn when physical attractiveness is plotted against level of bias - whether there is a linear relationship, or whether the effect (indeed affect) tails off (or even turns negative?!) at some point. i.e. whether things just keep getting "better" the more attractive you are.
I think that the quoted Cialdini text blurs the distinction between physical attractiveness and grooming.
I can well imagine that people react positively to a well-groomed person because of the values such care over appearance indirectly demonstrates (social intelligence/wealth/hygeine etc.).
A halo effect based on pure physical attractiveness probably has more to do with a net positive bias resulting from a complex set of sexual dynamics created by different combinations of male/female and attractive/unattractive.