My experience is, sometimes it works well, others, it just plain sucks & suicides the leading horses/men. So I typically just use the full charge broad front, it impacts more head on enemy casulties, and makes them rout faster.

As some of the others have started, I do not charge to break up their lines, I charge to kill them. When they rout, I keep the attack until it wont let me attack anymore, mowing down their retreaters as much as I possibly can, because if you dont, you'll just be seeing them on another battlefield, so kill them while you have the oppertunity.