I've been listening on the radio to some interviews with shark and ray experts. They say, based on what Irwin's scuba team reported, that the ray didn't "attack" him, but was simply acting in a defensive manner. Irwin was swimming above the animal, trying to get on its back (just like he does with crocs), and the ray flicked his stinger up and it caught him just below the sternum, peircing his heart. It was probably the only place, besides maybe the head, that one could receive a fatal sting frm a stingray. They say that Irwin probably died instantly and felt no pain.
I agree that he was greatly entertaining, and from what I've heard he was a passionate and generous conservationist, and a loving father and husband, and so his loss is very sad. That being said, I also have to agree with those who say it's no shock that he died in such a manner. It's a bit like that documentary "Grizzly Man." If you spend your days imposing yourself on dangerous animals, one of those days the animals are going to lash out at you. And generally, the animal is going to win.