also the average difference in damage between the longsword (4.5)and bastard sword(5.5) is 1 point of damage which is a 22% increase in damage. if you compare that to power attack which is
+2)with -1 to hit, half damage benefit (on average) with no negative aspect. the benefit isn't bad math mathematically. assuming 3 successful strikes per combat encounter and say 20 encounters at first level thats an extra 60 points of damage vs the longsword at level one.
and the extra damage from a bastard sword is not based on a standard action so you get that benefit with both standard attacks and full round attacks.