The function of this device is crystal clear, lock the guitar to your strap, preventing any nasty accidents.
The best feature of this particular model is how dependable the mechanism is. With other models, I occasionally run in trouble trying to release the strap; this one has always worked spot on.
What is the worst aspect of this design? Contrary to other models like Schaller's or Marvel's, this one does not double as a regular "emergency only" strap button. This means that if for whatever reason you are not enable to use your regular guitar strap, you cannot use another one at all (unless it also has a Loxx system or you have a spare one at hand).
Anyway, I am so pleased with the design, that I think it is worth to upgrade all my strap buttons and straps to this system altogether. It rocks!