This particular cleaner has been in my possession for less than a year. The choice was made after researching the device's performance, capabilities, and the cost/efficiency of the replacement filter.

Now, there needs to be a clarification regarding the specific devices. A cleaner consists of 2 main "parts". One is the device itself and the other is the filter. The review mainly focuses on the device as it is compatible with all Xiaomi filters.

- The touch screen is located on the top and displays the air quality, particles, temperature, humidity, and the operating mode. From the same screen, you can open/close the device and choose one of the three presets:
Night mode where it operates at the lowest rotation speeds.
Manual mode where it can be adjusted to the speed set in the mobile application.
Auto mode where you can create scenarios through the app on how it should operate. For example, if the air's PM2.5 is <30, operate at x speed, while if it is >30, operate at y speed.

Additionally, the screen supports gestures that can be enabled or disabled. This specific function can be completely disabled from the app.

- The design is a matter of taste and personally, I find it more beautiful than Xiaomi's classic square designs. The build quality is decent and I haven't noticed any yellowing on the plastics yet.

- The cable is located at the bottom of the device and at the back, around the middle, is the air quality controller. This one is relatively accurate in its measurements and has a quick response.

- The app provides a lot of information. The remaining filter life, On/Off scheduling, touch screen lock, 9 speed levels, and If/Then type automations.

Now, let's get to the issue for which I gave it 3 stars, which is the noise. What I noticed is that even at the lowest speed, the noise produced is annoying because it resembles the fan hitting something on the walls. It has a constant scratching sound that may not be too loud but is noticeable, especially at night in a bedroom. This sound continues and increases at all speeds until the point where the noise from the airflow becomes louder.

I purchased the device from a well-known store in Piraeus that collaborates with Skroutz and I contacted them on the first day of receipt. As they suggested, I took it to the store for inspection after describing the issue to them. Naturally and expectedly, they didn't hear anything and refused to exchange it! Even more naturally since the inspection was done inside the store and not in a quiet environment.

After the request for exchange was rejected, I decided to completely disassemble the device to see if there's something I can fix. The device was completely disassembled and I ultimately concluded that the noise comes from the motor itself.

I don't know if this is a normal phenomenon, something I'm almost certain it's not, or if I ended up with a defective piece.

Other than that, the filters are affordable and there are various options. At least the black one that came with it (equivalent to Xiaomi's gray) is particularly effective in air purification. It greatly reduces cigarette smoke and any odors in the air.
However, it is better to read the comments for each filter respectively.

I have had it for about 2 months now. It does its job and more. In the same category, you won't find a comparable product in other brands. In 30 square meters, it cleans the air in about 10 minutes. The detection is quite fast. Unfortunately, it won't eliminate odors but it will significantly reduce them (nothing is better than frequently ventilating the space, of course).
As for the noise, it is generally quite low except for when it is working at full power. There it might be annoying, but only for a short while, since it cleans the space quite quickly (and returns to normal levels).
The filters cost around 25 euros. It is a moderate price but overall worth it.
As for its smart side, I don't think it lacks anything since Xiaomi Home is quite easy to use and it also offers Alexa/Google Assistance connectivity.
Overall, I am completely satisfied.

Very beautiful in appearance.
It has a relatively short power cable.
I struggled to connect it to Wi-Fi and after a lot of searching, I had to change the Wi-Fi password from WPA2 to WPA in order to connect.
It detects smoke very quickly (less than half a minute) and increases the speed.
It takes about 10 minutes to clean the air from one cigarette.
At idle, it is completely silent, as soon as it detects smoke, it increases the speed and sounds like a small-scale extractor fan.
Manually, at the maximum intensity, the intensity is quite annoying, I don't know if it makes sense.
Whether it actually does the job, I will see over time and I will come back.

Update 26/12/2021
The noise at maximum is annoying, so I had to create an automation from the application so that when the indicator goes above 55, it goes into manual mode (which I have set to about 30%) and if it falls below 50, it returns to automatic.
This way, it takes more time to clean the atmosphere, but it doesn't bother me.

Do not attempt to wash the filter, it will not regain its powers, on the contrary, it will worsen significantly to the point where it works overtime without cleaning the air.

I replaced it with the xiaomi SCG4021GL, which is compatible.