Heavy cav is GOOD at fighting, and will kick the ass of any sword-wielding infantry, especially if they get a nice charge... but they are expensive and few in number and vulnerable to missle fire so I like to keep them out of the way until they're really needed.

Sometimes I charge them a bit ahead of my main force if the enemy is routing, or running because they are all skirmishers, and this can lead to some high losses for my horses-- but the huge number of enemy killed and captured usually makes this a worthwhile sacrifice.

DA