It really helps out with a small party. Even not neccessarily a small party. Your average four person party can benefit from it as well because sometimes no one wants to play the cleric (or some other healer) or the wizard (or some other arcanist) or the rogue or the fighter.
Also, everyone likes to say power gaming like it is a dirty word, but to the same people who say that I have to ask do you play to levels above 12th? Because around that point, and especially into epic, the WHOLE GAME becomes nothing but powergaming...so who cares if some people want to play at that level a little lower?