Player-controlled units exhibit remarkably stupid path finding skills for the most part, and the custom path selector is all but broken, making maneuvering in the battle field a hair pulling experience. Sieges are an absolute nightmare, with units opting to scale walls using grappling hooks when your cannons have already blown open the front gates.
Battalions are slow to react to commands, and will refuse to fire at an enemy 20 paces away until lined up in the correct formation. This means that if you are flanked from behind, you can forget about simply commanding your troops to fire at the offending enemy troops, as they refuse to do so until the entire formation has done a pointless 180 degree turnaround.
It is not only player-controlled AI that exhibits pathetic idiosyncrasies and your enemies are no less handicapped by idiotic unit behavior. Numerous times I was able to march around the back of an enemy unit and start firing, only to have the enemy in question stand and allow themselves to be submissively slaughtered without lifting a rifle in protest.