Comment Like the one in my basement since Oct 2019 (Score 3, Informative) 102
It does exactly what I got it for, and I'm happy with it. Since installation there have been 42 "events" with a total usage of about a day, the longest 3 hours. Most of the events have been ten minutes or so, just a few longer ones. It's kind of nice to find out about a power outage on my phone, then look out and see the street dark. (numbers off the app on my phone)
I've been in this house 40 years now, serviced by GMP. When we first moved in the power reliability was rather iffy. I'd started looking into a generator and sizing things up - then the reliability got much better. It was that way for a long time, then probably 10 years or so ago the reliability started dropping again. So when the battery option popped back up I was an early adopter.
A few notes that others have hinted about. It's not just a battery, it's got an ethernet cable into my network, so it talks to the utility. It's also got an environmental system built in for both cooling and heating, though sitting in my basement it stays at a pretty constant temperature. Because it's got constant monitoring GMP will know if things start to go south, and I suspect I'd get a notification on my phone. So it's not like the thing is suddenly going to burst into flames with no warning at all - there will at least be prompt notification. More likely it's not completely out of the blue and there are warning signs.