I have contemplated buying one of these. Brady is a hog and eats all his food within seconds, literally. I have tried putting the larger rocks in his bowl as suggested but it didn't really slow him down, he just worked harder and got the food down just as quick. He eats every meal as though he is starving and it is his last, bloat is always in the back of my mind.
I now just dump his food on the floor which works the best because the faster he tries to eat, the further he spreads it out. This way he is still done in about 2 minutes and of course this doesn't work when I mix in stuff with the kibble.
I think I may give this a try, sounds like it could be a Christmas present for Brady.