As the heading says, I tried a set of these years ago, and now I put them on everything I buy. I'm happy to be "limited" to this system, as I can still swap straps around between all my instruments.
Pros:
- they work, and they keep working.
- they're easy to fit, and can be removed wihout much trouble.
- you can still use a regular strap on guitars fitted with these.
Cons:
- the screw is pretty deep, so it sticks out a couple of millimetres from the back end of one of my guitars - I was just worried about splitting the wood if I drove it any deeper. I drilled a hole through a pick and used that as a spacer, as a workaround.
- once you've fitted a strap with the matching clips, you can only use it with instruments that are fitted with these, until/unless you remove them from the strap.
- they _feel_ slightly rattly, but I've never had one fail on me yet.