I've seen these for as long as I remember, but for some reason I've never considered getting one, or even used one.

It now occurs to me that it would have the advantage of being more easily detachable (which might also be a disadvantage, if done by accident!); but perhaps there would be a disadvantage (untested by me) of less stability than you might get from a conventional strap (if I may thus refer to a strap that attaches to the button at the body/neck of the guitar), i.e. the guitar might tend to swivel around the hook, which is the only point of support apart from the player's hands. I stress this is all theoretical as I've never tried one!

Can anyone who has used a sling, comment on whether they have found it worse or better than the other type, and if so give their reasons? Just interested to know, in case I'm missing out on something.