You just have to use them correctly. I took 10 tonight against high elves as i wrote elsewhere, and placed them out wide against his own flanking reavers and his archers. He tried to draw me away from these units by threatening a flank attack with his SoE's, but i just wiped out his SoE's with magic and shooting and then my CoC's were able to secure that whole flank, losing a single model to take down seven reavers and 20 archers before coming in to support the main combat.
They cost a lot but they also hit pretty darn hard with +1S on the charge with spears. And they are very survivable thanks to the additional +2 for being mounted. I wouldnt bother with a command unit in them tho. I flitter between taking just 5 of them or taking 10, depending on how i want to use them. In retrospect, 5 may have been enough to see off his reavers and archers tonight as opposed to 10.