Lewis Clemmens wrote a review of Petzl Grigri Belay Device on February 22, 2005
Yes, the Gri-Gri is bomb-proof for stopping a fall (almost too good, that bit of give as the ATC clamps down on the biner is a few less newtons on the back...). My belay partner is much lighter than I, and she can hold me with absolute confidence. That said, the only downside I've found is trying to safely use a Gri-Gri left-handed. With the smooth rope-protecting lip on the right-hand side and the brake in on the left-hand side, I have to either switch hands controlling the rope, or try to control the whole thing backwards.
Petzl needs to make a left-handed version of the GRI-GRI!