Hey, something I know a little bit about.
I do not use a standard blow gun and darts, I make my own (there is something special about tying your own darts). I do, however, have a friend who uses one so I am aquatinted with it.
I would expect maybe 100' of range. After that it gets incredibly hard to hit stuff accurately and consistently.
Some plus's about a blow gun is; silent, dependable, little movement when operating (with a slingshot you have a very large motion that you have to go through before shooting), darts are reusable and usually not that hard to find again, the ammo is small, because you use natural aim to operate it, it is very accurate... that is if you practice a lot and the whole unit isn't that big.
I am no expert, but I would use it before I would a sling shot. Of course, I am kind of obsessed with blow guns. lol
"This is my rifle, this is my gun." "This is for fighting, this is for fun." -Full Metal Jacket
"I joined the Navy to drink in foreign countries and fornicate." -unknown