I disagree that buttonheads are worthless. If you climb a route and need to pass a bolt that I have placed or clip it for a belay, I think you would trust that it will hold a fall. The interior width of a 5/16" rawl is only 1/4" I believe. I'd rather not take a shear fall on a 1/4" shaft that could have been stressed while twisting a nut around it to tighten it. I have seen the nut shear the shaft without much effort at all in a controlled situation. (meaning at home in a vise rather than in the mtns) If a 5/16" buttonhead is placed wrong and the head bends before it mushrooms over the hanger, they are less reliable than if it is hammered straight in. I think skill is what makes them bomber, not the nature of the material.
I will continue to use 5/16" buttonheads until they are not available. They are in fact, bomber and I trust every one that I have placed.
I also apologize in advance if it sounds like I am chestbeating. I am only stating my opinion based on my own personal experiences. I don't think that everyone should follow my lead when it comes to equipment selection since it is simply a matter of style and opinion.