As title. I don't get why he seems so popular, as a tank he doesn't actually seem that good, and for the heroes I play most (DVa, Widow, Reinhardt, Ana, Pharah, Soldier) he's a pretty easy kill, and not much threat. He has his one trick hook, but doesn't seem to offer a lot outside of that or his ult.
Admittedly I've never played him, so maybe I'm missing something but I don't feel like he's a major problem to face and I hate relying on him as solo tank on my side.
So what's the fuss about?