I would use it if the cavalry charged straight into the enemy unit. But because most of the time it swings to the left and pretty much goes no-where, I don't bother. Often it is better to use a standard charge, or a long thin formation that will overlap the enemy unit and cause carnage from multiple directions.

However, if ever you find yourself with head-hunting maidens and you're going up against Cataphracts, use the wedge, but click behind the Cataphracts. It's the most efficient way to kill those tanks with those ladies. I've done enough tedious tests to find that out.