Top critical review
Returned it for several reasons. See tp-link website for install video.
Reviewed in the United States on October 15, 2020
Recognizing most reviews indicate satisfaction, I'm sorry to say the switch did not provide the extra flexibility I was looking for. After the switch arrived, I found Amazon reviews that I'd missed earlier, making clear there would be difficulties for the application I had in mind. The packaged instructions dwelt only on how to interface with the Kasa app, nothing about the wiring. I went to the tp-link smart switch website. The install video warned against proceeding if I was not an experienced electrician. I have installed a few other smart switches of a different brand, but not for the type of switch I was looking for.
This switch is designed for two and only two switches on the same circuit. Only one "smart" switch is needed. In this case, you can keep one of the mechanical switches. There must be a neutral (usually white) wire available where the smart switch is installed. From the reviews, I take it the switch gets out of sync with the positions of other switches in a multiple switch circuit. I've seen reviews citing the problem even if there is only one other switch. Personally I did not find the install video very helpful as my switch (on a circuit designed for 3). It wants a line/load to be connected to a single point - my switch has two wires fastened together at the switch to where I found a constant voltage of 124v, but it did not look like the configuration I saw in the install video.
I tried the web chat feature, it wasn't working on a mid-Thursday afternoon (EDT).
Originally I had a different circuit in mind, but I needed a dimmer capability. This one doesn't have it, although it showed up in an Amazon search where I had specified "dimmer". My bad for not double checking. So much for almost nil customer service.
Thankfully Amazon made the return easy.