Any flat-footed Major League first baseman can hit for power (which, by the way, Millar doesn't do). In fact, they are EXPECTED too. Aside from A-Rod/Tejada/Formerly Nomar, any offensive production from a SS is generally considered a bonus.
Renteria's and Millar's numbers are virtually identical, except Renteria has done it in roughly 100 more at bats. Neither is a goat (although Millar often makes an ass of himself, so I guess I should so donkey), and neither is a god. Let's leave it at that, ok?