I have bought a total of four. I have had the first two for two years, and they still work perfectly. Sometimes it may take 3-4 seconds for the notification to arrive, but that could also be a network issue. One is two rooms away from the router and works just fine. I will definitely buy again.

Very good product! I have had it for a year now and it works perfectly. During this time it has disconnected 5-6 times, even though the door where I have installed it is 2m from the router. With alkaline batteries it lasted about 7 months. I recommend it!!

It works properly, of course a big problem is that its battery lasts 14, 15 days so it is useless.

It does its job just fine.... I've even added a siren to it! (Indoor Alarm Siren 230V)..... I've connected it with a Sonoff Basic R2 Smart switch and it works perfectly!
I bought 3 more and with eWelink, they work very well (for now). I've programmed them to operate during the hours when I want security.

Attention, it does not work with Starlink Internet, at least I was not able to set it up.

When I got it, it worked perfectly and connected the first time without interruptions or anything else.

Then I switched to Starlink and since then it never connected, I tried many times but nothing!

Functional sensor, with connection to a mobile app for monitoring, activation, and alerts.

It is almost impossible to pair it. I managed after a lot of effort without any obvious problem. A year later, I needed to change the router and it never paired again. The problem seems to be with the WIFI bands. If you have a 2 band network, you need to disable the 5ghz, but still, it didn't pair. The eWelink software is very bad. 1/5 because I can no longer use it.

I don't know about battery life. Time will tell. On the negative side, there is a small delay in status change notification. The biggest problem is that it only supports 802.11b (WiFi from 1999 with 11 Mb/s). Modern routers no longer support it. It is obsolete!

1+ Year of use
At first, it worked perfectly and with the trigger on the Echo Dot to announce when the door opens and closes, but after a while, the batteries would drain immediately and it would malfunction.
It's a shame because it could be a must-have for any home considering its price

Waste of money, it constantly disconnects and doesn't send notifications. I have four, one of them is currently connected.

Good, it doesn't freeze, works quite reliably.
The only downside is that through the internet, if you're not at home, the notifications are delayed (and sometimes half an hour).

I have installed 6 or more on a deco system with excellent coverage.
1) Several unnecessary disconnections in some cases, more than others... not reliable here.
2) Batteries: regular AAA batteries are consumed in 3-4 months. I will try alkaline and rechargeable batteries.
I will also look into the issue with the channels, although it is an acceptable behavior...

After about 2 years of use, I have to say that it does its job perfectly. Battery replacement is needed approximately every six months. Sometimes it takes a while to respond (10-15 sec), but I suspect it's due to the router, as it is provided by the service provider. Also, due to the heat in the summer, the double-sided tape softens, and the battery compartment slides as if it's heavier, resulting in it entering the on mode. That's where it requires a little attention..

As others have mentioned, the connection is frequently lost and you have to reconnect with the application from the beginning. It's better to go for something more reliable.

Immediate response from the ewelink app.
It takes 1-2 sec to give the command to run a routine through Alexa.
When connected to wifi, I notice a decrease in speed on the 2.4 GHz from around 70 mbps to 2-3.
I don't know if it happens to others or if it concerns the 802.11b protocol.
Based on the above, I do not recommend it.
I also read about disconnections, but for me, it was flawless with no disconnections.

For 2 days it worked great! Then it started losing connection with the router. I changed the batteries, I changed its position, but still nothing. You make the connection and after 2 hours it gets lost

I would also like to add my experience.

Initially, when I had connected them to the Cosmote router, I also had constant disconnections and they even affected my wifi connection (excellent on wifi, etc., while the wired connection was fine).

For home cinema purposes, I had to purchase the Ubiquiti UAP-AC-LR access point and when I connected them to it (a total of 5 traps), I completely stopped having any issues. A year later, I didn't have a single disconnection, so I believe that MIMO technology in wifi plays a big role, as well as a good access point, in order to have good connectivity with all devices, especially if you have many devices at home.

In conclusion, in my case, the problems were solved when I upgraded the access point.

WARNING!!! As another user mentioned, the Wifi only recognizes the 2.4ghz frequency and only 802.1.1b. Otherwise, it does not connect.
After two weeks of use, as other users have mentioned, it disconnects daily and you have to remove and reinsert the batteries to reconnect.
EDIT: After one month of using it with a different router, it works fine.

Very easy to connect to Wi-Fi and with instant notifications. But it has a serious problem. It disconnects on its own. I have three of them and every 3 to 5 days, one or the other or sometimes all of them stop working. From working normally, they suddenly go offline and you have to restart them or the router for them to work again. Something that is not easy to do every now and then. I would not recommend it.

P.S.
To preempt you, I have them in close proximity to the router and none of my other Sonoff devices have this issue, only these ones.

4 such sensors were purchased. Initially, there were disconnection issues, but they were probably overcome when I changed the router's channel from auto to a specific number. Additionally, the repeater's network was also separated.

So far, it has been 10 days and I haven't had any problems.

Finally, after 12 days, it disconnected again and now it takes a whole day to be activated.

As of 13/3/2023, an old technology router is required, only supporting 2.4GHz and the option of 802.1.1b.

Unacceptable device for this company. Not for its functionality, but for its power supply with 2 AAA batteries. After about 40 days, it needs battery replacement. I was forced to use an external CR123 battery.

I have had it for 5 months and it works quite well. I haven't changed the batteries yet and its level is from 3.1 V to 2.75 V

Very easy to connect, immediate response, I bought 6 pieces and none had any issues, neither with the batteries nor with disconnections, maybe there was a defective batch for what other users write.

I have 20 of these at home and I don't think it's a coincidence that it happens to me. Yes, it is very easy to connect to the positives, yes, you can do many things with little money, but it constantly disconnects and reconnects, one breaks and another one needs to be set up from scratch. Out of the 20 that I have, none of them work together, also many times they are slow in their notifications and of course in the routines that I have set up. For the record, out of the 20, 3 had problems from the beginning. For someone looking for simple automation, it's okay, you can do it again, but for someone who wants it for triggers in a routine or for an alarm, I would suggest looking for something else.

It consumes a lot of batteries and does not have settings in the application.

Very easy to install - use - connect!
Sends a notification if the door opens even by half a centimeter

The best for the 6€ it costs! It works as a trigger for Alexa and you can do whatever you want with it. Now, as for the range that others say, I don't know, I have it 5 meters away from the router and it catches perfectly without any problem. The set up is very easy and the application is very good, which I didn't expect, you can sync it with the Alexa and Yeelight applications, and it automatically detects all the smart devices you have. I will definitely buy another 2-3.