I've killed a bunch of deer, a wild hog or two and an Asian Water Buffalo using FOB equipped arrows. What I like about them is the arrows will experience LESS wind drift with FOBs over vanes or feathers. And they do stabilize big two bladed broadheads I think a little better than vanes.
They are somewhat pricey however and if you shoot with any degree of accuracy, you'll have to shoot a 5 spot target or you'll start tearing them up.
But they do work as advertised.
Formerly Steve @ G & S