From a UK-based A320/1 operator:. .. .Every sector, both pilots (Capt or F/O) have a complete role reversal (tech log completion, walkround, FMGC loading, pushback and taxiing. There is no job an F/O or Captain cannot do to the same standard of proficiency as the other. Obviously the Captain is usually more experienced than the F/O but both guys are expected to be up to speed. The only limitations come on weather (Capts may take-off down to 125m vis but F/Os have to have 650m. Also crosswind limits for F/Os are 2/3 of the Capt's) . .. .It works well, and the issue of whether the F/O is up to the job of taxiing simply does not exist.