God, the Dragon Shaman in our group LOVES the class. He took his first level in fighter so he could get a tower shield and heavy armour proficiency, making his PC an AC monkey. Right now, that "AC Monkey" role is really his primary job in a fight - people try to hit him, while the goliath kills everything in his path.
He gives everyone DR 1/magic in a fight, which really adds up (one less point of damage each time you're hit adds up at low levels) and his ability to heal the group to 50% of their max HP at will really increases the cleric's healing abilities (meaning the group can stay in the fight much longer). Also, he knows that even one round of his healing ability will stabilize people at negative hit points - a real life saver.
He's currently counting down the levels until he gets his breath weapon; very excited about it. I know the whole group loves having the shaman around - he does make the group much, much better, and he's having the time of his life doing it.
I wouldn't say it's overpowered or anything (in comparison to, say, the war mage that the player once ran), but it's definately a great character to play. Seems to work well in the group (I personally think bardic music work in a way similar to the dragon shaman's auras)