I've ridden Buffalo Mountain,Rockhouse, and am about to ride the southern most 3 systems that connect to one another next weekend. They are Indian Ridge, Pinnacle Creek, and Pocohantus.
Buffalo Mtn is a very good system. Didn't ride all of the blue and green trails because we just didn't have time, but, it was very fun. There is a place called the "play ground" where you can do several hill climbs if that is your thing. If you stay there DO NOT stay at the Boars Nest. That is where we stayed, and it left a lot to be desired.
Rockhouse, in one word, AWESOME!!! Yes, it live up to it's name, there are lots of rocks. But, once you get used to them, you don't even know they are there. Pretty much the really bad rocky trails are all on the left side of the system. Trail 31 is freakin KNARLY! You'll go probably a 1/4 mile up the side of a mountain that is all switchbacks, that you will be powersliding around the corners, and cramming the throttle once around it. THE most fun trail I've ridden out there. The rest of the system is awesome as well. Lots of challanging trailing, fun, interesting, and some of the best views. If you want a really good place to stay, call up Browning Fork Trail House (if I'm not mistaken). That is where we stayed, and are planning on staying there this June.