Since dropping my guitar once and having to mend the headstock, I put these on all my guitars.
PROs: elegant system, easy to install, hasn't let me down once.
CONs: the knobs do protrude quite a bit which causes them to touch the ground when I put the guitar on a stand. Also, the system isn't completely fool proof: you have to make sure the guitar-part is completely down into the strap part or it'll end up falling off. Never happened to me though, I'm extra careful now. Also, they're not the cheapest solution.