The thorn in my side is the alignment restrictions, particularly when it comes to Rage. (You have to be non-lawful to Rage, you have to be lawful to be a monk or a pallie.) It seems only to exist to neuter Barbarians who multiclass to either of those two classes. I could see it if Rage were some kind of mindless kill-frenzy, or if monks and pallies weren't supposed to be good at knocking heads. I don't know, it might be fun to play a barbarian who mulit's to paladin who then has to atone every time he loses his temper in battle.