The real problem with a PLB is that the average person knows nothing of their existance, let alone when they should own/use one.
I cannot justify the cost unless I plan a really remote trip without communications available. When you consider that the PLB is basically a simple single frequency transmitter that can hit a satellite, it seems very overpriced. There are a few other negative aspects, they are not very waterproof considering their intended use, they are heavy of you plan to backpack it, in realtive terms and they use proprietary batteries that must be factory serviced every 5 years.
Yes, they could save your life if ever used in an emergency but how many of us have $700 to invest in one? I honestly doubt I will buy one in their current design. It would have to half in price, come with better weather resistance and have self service batteries, like CR123s. The concept is excellent, just not very affordable for the masses.
Compared to a GPS map unit, or a HAM radio, a PLB is like a tricycle compared to the space shuttle, yet the PLB is much more expensive. I do not understand that aspect of the PLB.