Apparently it's not that. I can't even kill them with the guisarme. It's possible I'm just not remembering correctly from years back, though. Edit: I think the only real issue with it is that you can't get experience from subduing opponents (as far as I know). I kind of wish more things like that were accounted for, but this probably isn't the game for it
Well, it says it works like polymorph 'except ...', and doesn't mention more abilities in the exceptions. I have no real interest in that spell, though. Normal polymorph is already really complicated, and the additional rules for PAO make it plot device territory. The only part that seems like it'd actually be reasonable to do without some kind of story integration is the last one where it can replicate a few other lower level spells.