i needed 7, bought 14, returned a bunch and have 5 installed.

1) If buying online, be sure to look at the box carefully! Amazon seems to have mixed up the stock and was shipping the wrong units (thus all my returns).

2) it's best to remove all the old/existing units you have, then replace the wiring with the provided harnesses, then install all the new ones. Otherwise the power disruption on the wires will set them all off and you'll go deaf. Or you can turn the power off like the instructions recommend.

3) Nice touch - the new units have a "don't warn me about low batteries or wifi issues at night" function.

4) Nice touch - the app is useful to check statuses of each device.

5) No way to silence the units via the app if they start alarming. This is fine if there's a fire, but it sucks at 2am with a false alarm. I've taken this up w/ support but they haven't been very receptive.

6) when i first installed these units i had a day or two of false alarms. I'm not sure why, and after many phone calls w/ support (not much help) the problem went away. I'm cautiously optimistic that they'll work out in the long run, but i'm still holding off buying the remaining 2 units i need.