I too am an ACR owner.

Two thoughts:

(1) Don't forget that PLB's have a finite (limited) lifespan. I think the expiration date is 6 years from manufacture date, though the battery may be viable for several (3-5?) years after that. Plan for this in the overall cost of ownership. For my older style PLB I found the cost of battery replacement to be too high to justify. I was better off just buying a more modern (smaller and easier to use) PLB.

and

(2) It is VERY important to register the PLB and make sure that the correct contact phone number is listed, and to keep the registration up-to-date over time (which to be honest can be kind of easy to forget to do).

If the PLB is ever activated someone will be calling that contact phone number to confirm the viability of the activation.

Here is registration website in the U.S.:

http://www.sarsat.noaa.gov/beacon.html

On a slightly different note, I chuckle a bit when I read the oh-too-common PLB vs. Spot arguments on other forums (there was one recently on a Boundary Waters Gear forum), in which people quite literally get angry and seriously defensive about their choices. To me the two devices have very different uses/objectives. The Spot is a communication device that might help you out in an emergency. The PLB is the emergency rescue device that you can trust with your life.