Not a first belay device
I took a belaying class awhile back which they taught with the grigri. While the autolocking feature is pretty much fool-proof, I found it rather difficult to control the speed of descent. After the class, I ordered the ATC and started climbing with it. I found it much easier to use than the grigri. While I'm sure the grigri has a ton of great uses, I would just advise beginners out there that a cheaper atc-type belay device is money much better spent when starting out. Once you progress, I'm sure you may someday benefit from the grigri, but it'll never replace the atc. Also, in regards to teaching new belayers...an auto-locking device should never replace another experienced belayer at their side.