Hi, George Hill,
I have never seen anyone beaned by an M9 slide breaking off, but I have seen cracked slides, so it sure has happened. Many criticisms of the M9 have not been valid, and others are actually of the cartridge, not the pistol itself. The Beretta is not a bad pistol, and has proven reliable, but it is not perfect and not deserving of blind defense.
I just don't buy that a big heavy pistol is the best for military use. A military pistol (aside from being a symbol) is primarily for last ditch, emergency use, not for shooting enemy soldiers at 500 meters. I think the Russians had the right idea with the Makarov; a light, fast handling pistol for the time when the tent flap opens and some guy in the wrong uniform sticks his head in.
Of course, Americans always think of a military pistol as something that can be "accurized" for use on the range. They have that in the M1911/A1. But range accuracy is not really relevant or necessary in combat, especially if it means reduced reliability and increased weight.
It has been suggested that two pistols be issued. One would be a light Makarov style pistol for high ranking officers as a symbol and emergency weapon; the other would be a light submachine gun, like the MAC 10, for use by troops who have to carry or man other weapons. The latter would be light enough to be carried on a belt or shoulder sling, but would be more effective than any conventional pistol. It is, as they say, an idea. (Of course, it is the old "carbine" concept all over again, so there is nothing new under the sun.)
I will stick by what I said; the M9 is just too big for a medium power pistol cartridge.
Jim