Also it gets the rust out of the eye which is a tad trickier to do with power tools.
And the stuff is reusable... I have a small cube-shaped bucket that can hold one or two axeheads. I just pour a gallon of vingar in there and let heads soak for a few hours. After I'm done, I'll pull the heads out and clean them off. By the time I'm done with that task, the rust will have settled at the bottom of the container and I just use a funnel to pour the vinegar back into the jug for later use. Eventually it loses the needed acidity to strip heads of rust, but there's no reason you need to go out and buy a thing of vinegar for every time you restore an axe. Probably more practical for someone like me who finds the need to fix one up every month
The main reason I prefer vinegar though is that it shows you the temper line, as bax mentioned above :thumbup:
Figured I'd snap a picture of how I do it since I'm currently filing up a head to haft. Folded up paper towel in the eye to prevent the clamps from marring the inside of it. Simple, cheap setup and the head is immovable from the desk...