Well, I use them all the time since I didn't like Saurus back in WFB and I decided to make a Ghkkotah themed army in KoW. Problem with them is that they are a bit overpriced, I really think they should have another special rule, probably pathfinder. BUT, if you use them well they can be good, you obviously can't use them as your main battle line but used as chaff or bait for other units they are good. Also if you use them to flack charge deployed at the sides of your main units they can really pack a punch.
That being said, I usually use a Horde in low points games or two regiments and a horde in higher point games, and the horde usually performs decently. I like to throw the horde in front of the hardest hitting unit the enemy has (the highest CS or TC the better), with defence 3 they are overkill for them and thus they are wasting that powerfull unit destroying your cheap unit and with nerve 19/21 they can hold them at least or two turns. Its beautifull to see a Soulreaver cavalry being hold by them and then getting flank charged by my tyrants.
