I've had one for a year+. I've used it in S. Idaho, Western and Eastern WA, and Central OR. The only place that I"ve had an issue was in the big trees in the W.O. Douglas Wilderness. The service was spotty, but when I broke out into the open, it acquired a signal within ten minutes. That is slow by GPS standards, but a reality with SPOT.
I don't know why, but I'm still getting service after the one year anniversary and I only paid for one year of service when I signed up. I keep waiting for an email that says I need to pay again. The device keeps working...