For those uncomfortable with deformed bird-woman nudity, an alternative picture can be found here.
Harpies have seven monstrous humanoid HD. Their fly speed is on the high side, but their ability scores are disappointing for a mid-level creature and their natural attacks are mostly useless without a source of bonus damage (though they can be used with a wielded weapon).
Captivating Song is difficult to read. If it's a (Su) ability, should it be a standard action to activate? Does it take a standard action to use on each next turn? If so, why does it specifically say affected creatures don't resist the harpy's attacks?
Even the most favorable interpretation doesn't change the fact that a moderate SoL has been available to many other classes for a long time now, though. -0 seems to be the only fair LA.
Next are hell hounds.