Having just finished a games against a Tzeentch flying circus (didn't expect to play that today!) and a 2nd Gen Slaan list I've come to the conclusion that Forbidden Lore rocks in all ways, shapes and forms.
This realisation came in two parts, the first after watching the slaan drop into a Pit of Shades(so much for that damned hoverchair), and then watching my Count get charged by a Lord of Change and promptly headbutt it into the ground while enraged by Bear's Anger. These proved to be pivotal moments in each game, with each being beyond the scope of normal VC tactics.