A lot of these trails are easy doubletrack. But, there's a lot of really cool single track branching off. I go here once a week. It's a little small for my taste, but it's nice. Not too hard, not too easy. Some of the trails are a little hard to find due to the construction that's going on. Some are actually no longer in existence in parts, but, with a little work, you can find your way.
Night riding at specific times, with approved leaders only.
From 85 North, take 316 to Grayson Highway (20). Take a right. Take 20 to Scenic highway, take a left. Look for New Hope road, take a right. Stay on New Hope for about 5-6 miles, take a right onto Tribble Mill Parkway. Park Off the side of the road just across the big red bridge, or keep going around the circle to the parking lot.
http://www.singletracks.com/item.php?c=1&i=598