Besides Plot twists, Victims, and hourglasses, the base mechanics are pretty much the same. The dials are organized the same way with speed, attack, defense, and damage values. Both systems rely heavily on the character cards to know what abilities/certain powers do. I am sure that if you are comfortable with the action & combat system of heroclix than you can pick up horrorclix (namely the unique points of that system).
I'll wait for Boogy Man to give a more detailed break-down.