A must for beginners who haven't learned to disapline themselves and pay attention while belaying. I'm not saying it's idiot proof but works better than a non-camming device. The lever arm takes some getting used to when lowering. I bought mine in 1997?? and it was the coolest looking thing around. Still works great.

My opinion is that for gym climbing this thing saves people from getting hurt by incompetent belayers, cause it's almost idiot proof, and if all goes well (which it usually does) it will catch even if somone isn't paying as much attention to you as to the blonde climbing 2 routes over from you.
On the other hand for outdoor use I'd never let anyone use it to belay me (while on lead) cause you can't feed the slack out properly without lots of practice, and there's no chance of a dynamic catch.
Other problem is the limited rope diameters that you can safely use with this device.
Oh....and it's kind of expensive.

I give only a four because it has its place, but should not be the first belay device. I think it rocks for TR climbs, but very crappy for lead belay. If you gym and TR - get this and don't look back. If you are heading into leading...might want something else or just get both devices.

I love the GriGri.
Great for teaching belay.
It's worth the $$$.
I wish I had 2.

don't think that just anyone can use the gri gri. Though the auto lock feature is nice, it takes a bit of experience to learn how to use it properly. Use caution.