Seeing a fresh "What's wrong with XD's" thread added in another place, I figured I'd add my personal experience.
In various training venues, both LE and "Normal Earth People", I've personally seen two XD's lock up during shooting, due to something malfunctioning inside, possibly, the grip safety assembly. The grip safety's normal function of locking the slide from moving is a definite no-go for a serious use gun, in my opinion, as it makes various gun manipulation tasks under stress much harder.
In high round-count classes, I've also witnessed two different guns shear the roll pin that retains the firing pin. The shooters noticed this by seeing the little broken pin half poking up from the slide top. This didn't stop the guns from firing, but it points to a serious design/manufacturing flaw.
By way of comparison, I've seen Glocks, M&P's, Sig 320's, etc, in high round-count environments that exhibited none of these flaws.