AoO whie Concentratiing?

[TYPO5478]

My vote too.
But I figured I'd post the question to see if anybody disagreed and could tell me why -- there are a few players in my group that disagree but all they can come up with is that it doesn't feel right to be able to make an attack while concentrating on a spell.

That's a lousy excuse. Arguments based on visceral emotional reactions are nearly always secondary to arguments based on logic and reason.

A caster doesn't spend all of her attention concentrating on a spell; she only spends one standard action. At least, that's what the rules say.

Sometimes a combatant in a melee lets her guard down. In this case, combatants near her can take advantage of her lapse in defense to attack her for free. These free attacks are called attacks of opportunity.

If someone lets their guard down enough to provoke an AoO from a caster concentrating on a spell, there's no reason the caster can't make the attack.