Just bought a seat of the pants, and glad to see it is well liked.

My advice is make sure you get a full body harness. Makes sure the buckles are quality. Slid one time climbing a tree and the saftey belt caught me, but afterwards I saw the buckle was almost broken, if I would have had to hang there a few minutes it would have broke. With the full body harness make sure the tree strap comes off the harness higher up in the back and not at the waist, cause if you fall hanging upside down won't be fun, if the strap is higher, more of your body weight will be below the strap and you will stay vertical.