A great place to mountain bike. Has some great technical single tracks and hairy switchbacks. Plenty of areas where you'll run into some pretty rocky terrain on your descent. Definitely not a place for beginners. Giant Salamander is an awesome trail. Although this can be done on a hard tail, a full suspension bike is highly recommended. You'll basically be riding down into a big bowl so wherever you ride, there is going to be an unpleasant climb back up.
The hiking was pretty decent, but the description doesn't lie when it says that the trails are used primarily for mountain biking. There were a lot of cyclists blazing past us until we turned off on one of the steepest trails to go down into the gully. Nonetheless, it was very enjoyable.
Jessica D. on Tafoni and Fir Trail
Great trail, although it does share with a mountain bike trail, so keep your eyes open for the bikes (they come flying down the trail in some cases). The Tafoni formation is truly an amazing site.