The GriGri is an excellent tool for many uses. I use it as a personal tether when setting things up, ascending ropes, rope soloing and it is especially useful hauling. When hauling it acts as a pulley and auto-block, negating the need for a pulley. Rappelling with it can be a problem, but it's great for simul-rappelling. If you're not careful with new belayers they will learn bad habits from it. I still recommend teaching new belayers with an ATC when a good learning environment exists.