Rowdy,
from what I've heard reported from people who have used them, they eventually have problems with shrinkage and leaking from being used and then drying out in between use. Most are coated on the inside with food grade canning wax, which can eventually pick up musty flavor and should be recoated every once in awhile.
I still like their look, though, and they scream out for adding your own personal decoration. There is a shooter in our club, Annie Noah is her alias, who is an absolute artist with wood-burning. I would love to see what she could do with one of those wood canteens! Trouble is, I'd be afraid to use it. It would go on the mantle.
(At one time I was going to use one of them, or one of the miniature casks used as canteens during Colonial era (James Townshend, if I remember sells them) as a container to hold cleaning solution in to dump dirty brass into during a match. You can get large corks at gourmet shops that are for wide mouthed containers, and I was going to cut a larger hole with a circular saw bit used for mounting door hardware, then take the cork and wrap it with sandpaper for final chamfer and fit. But I never got around to it. Just as easy to throw the brass into a satchel and clean it when I was home.)