Except, once again, in the case of a succubus, they can *only* polymorph into humanoid form. No hill giants (thanks again, Hyp

), no bears, no thri-kreen, etc. No "massive strength bonuses, special attacks", etc. I still say that Succubi would have been better off with Alter Self being limited to humanoid forms only.
What's that? Alter self only allows changes between your type? Well polymorph allows any type, but not in the restrictions of succubi, so that arguement is out. If you're going to muck with Polymorph's normal rules, you can also change Alter Self's.
And, when you're looking at the type, there aren't *that* many types of humanoids that are better, statwise, than a succubus, and many of those would stick out just as much as her natural form.