The charge bonuses are rather large for some units in RTW. Greek lancers get a +15 charge bonus Round shield cav only get a +2 charge bonus. You probably wouldn't want to use wedge for frontal attack with cav unless you have a substantial charge bonus or heavily outmatch the other unit, because you will take casualties at an accelerated rate as well (I believe.) You might charge, then enter melee to hold them, while another unit charges into their flank or rear (with wedge if you like) and rapidly routs them.

Countercharges are imperative for many units. You stand a good chance of negating a charge by countercharging. Caesar said that it was best to countercharge to bolster the men's morale, rather than stand there and take the charge. RTW seems to be designed with this in mind.