I bought it yesterday 5/5/21 at the regular price of 469€ (-112.56 due to VAT exemption, not at that moment though (in the quarter), -93.80€ due to store offer card refund, so it actually cost 262.64€). I am explaining this because some of you might want to take advantage of it.
The device is very good for its price in terms of mid-range devices. The speaker/sound quality is very clear compared to other devices where you can't hear well. The screen is Amoled, so you understand the advantages. I would prefer it to be Super Amoled like the Mi9SE had.
What impressed me is how lightweight and thin it is compared to others in its category. The battery lasts for more than a day with regular use, but I will come back to this later. It runs on Android 11 and is preparing for 12 from what I read, which practically means it will bring more features related to 5G. I haven't tried 5G yet as I need to change my SIM card first and be near a antenna (my area has it). The camera is at a very good level in terms of photos and videos for the cost of the phone. The only thing that bothered me is that in order to take 64mp photos, you have to select that specific mode, meaning you can't immediately take photos at the highest resolution.
As a test, I opened over 60+ apps to test the RAM and processor. I played Subway Surfers and NBA games while having all these apps open, and I didn't experience any lag, just a slight increase in temperature at reasonable levels. What impressed me is how quickly the temperature dropped as soon as I cleared all the apps. The fast charging is also very good, it charges quickly. For its price, it is worth it, so 5 stars. Xiaomi has proven that it can provide quality with relatively low prices. Finally, I want to mention that I have tried/used several Xiaomi/OnePlus devices (my favorites), but OnePlus has gone too far with all this marketing. 1000 euros for a phone is too much (okay, it has perfect specs, but we won't feed China every now and then just because they release devices frequently). Currently, the best choice would be the Huawei P40 at this price, IF IT HAD Google services, it is an amazing phone with a great screen. But what can you do if you don't have Google services.. endless bugs!! That's it, I hope I helped once again. If not, shame on me :D I wasted so much time writing this? Good health to everyone!
Edit: 7/5/21
The battery is very good, I always have Wi-Fi/4G/Bluetooth on for wireless headphones, the screen is at 90hz with about 70% brightness. Two things that still impress me are that it has a very good Wi-Fi/Bluetooth network card, never disconnected, always full signal, and the headphones haven't disconnected once in all these days. The connection is really fast, about 1 second for both the headphones and the car (speakers). I am also uploading some screenshots that might help some people.
Edit: 10/5/21
Until today, with extensive use, I can say that I am fully satisfied and the device is value for money (at the price of 450€). I gave the SK to my son to play Subway Surfers and after a while, I played too :D (to show him who's in charge, of course). The device didn't heat up at all during the whole situation, even when I initially set up the phone with around 60 apps installing simultaneously.
I would also like to share another opinion about the side button that has a fingerprint sensor. Well, it's AMAZING and super convenient. I've seen some OnePlus, Samsung, and Huawei phones before that were very responsive, and then I had the fingerprint on the screen. I can say that it's so fast that you think it has unlocked the function before you even touch it. Awesome. Perfect for finance/banking apps!
Edit: 11/5/21
I'm glad that you found my review useful and that it has practically helped you. Something else I would like to share is that the size of the device in my pocket hasn't been very convenient for me. This is purely a matter of habit, taste, personal opinion, you know. It doesn't have anything to do with any negative aspect of the device, it's just my own issue. The previous phone I had was 6 inches and it was perfect for my hand. The current device is lighter, thinner, and bigger, so maybe it just takes some getting used to. It's flawless as a device, and one thing I like is that in most apps, I can get all the information at a glance without scrolling (the advantage of the size). However, I repeat (for the second time again :P), it's a bit too big for my hand, sometimes I feel like it's about to slip. For people with larger palms, it's probably perfect, just like a 6-inch phone is for me. My conclusion is that it needs a good case + tempered glass, otherwise, I'll keep it in my bag.
Edit 24/5/21
Personally, I noticed that when I take the device out of my pocket in 90% of cases (as if my finger does it on its own, my goodness), I hold it in such a way that my thumb immediately unlocks it. Solution: I hold it differently and in a different spot. €50.
One negative thing I noticed in this Android version (not necessarily a negative of the device) is that you can't see the duration of calls. You can see when you called someone in the call log, but not for how long. This is something very useful for me. I hope they change it with an update.
Edit 7/6/2021
After 1 month of using the device, I can say that I am very satisfied and nothing bothers me particularly. (By the way, the device says the same about me :P :P)
Fast charging, long battery life, no lagging (I noticed it once, but it was an issue with the app due to many pop-ups), a beautiful, elegant, and powerful device. It practically hasn't disappointed me in the past month (except for one time when it raised its voice :D), it meets my daily needs. If I had gone for Samsung, I would probably have all these features for at least double the price...
Advice: I recommend you to make the purchase, but always be careful about where you buy it from, as there are many refurbished phones circulating at low prices. In my opinion, go for a new device!
Edit 8/6/2021
The device has been upgraded to MIUI 12.5.1.0 Stable and several functions have been improved. The graphics on the welcome screen and the pop-up graphics with the volume buttons have also been changed.
Edit 27/7/2021
After almost 3 months of daily use as my main device, I have to say that it never let me down. The fast charging helps so much that you almost never run out of battery. I am very satisfied with the camera in normal lighting conditions. Also, for those who love selfies, I can confirm that I tried using a selfie stick with a 3.5mm mini jack to USB-C adapter and it worked perfectly. The fingerprint sensor always works smoothly, no lagging. Wifi/Bluetooth connections are seamless, NFC payments and synchronization work flawlessly on a daily basis without any issues.
I also want to mention that my phone has fallen twice from a height of about 1 meter with just a simple silicone case and I didn't have any unpleasant surprises, thankfully. It is definitely worth the money, especially now that the price has dropped. I am attaching a photo of a sunset that I took with manual settings. Lastly, I only managed to get a 5G signal in specific areas of Thessaloniki with a very small coverage radius, but the speed was impressive! I'm glad that my evaluation and comments helped almost 200 people in their decision to purchase this device (although it's not a car, let's be honest... the analysis I've done is as if someone is buying a house! :D However, I know, like most people, that money is hard-earned and we all want to make the most informed and wise decisions in our purchases.) If anyone has any questions, they can ask in the questions section and I will try to respond at some point.
Update 13/9/21
I continue to update the review as I see that many people have been helped, which makes me happy! There is more joy in giving than receiving :)
A few days ago, the phone flawlessly received the highly anticipated MIUI 12.5.5.0 Stable update, which fixed some system instabilities caused by certain apps (some users reported it, personally I didn't have any issues). Personally, I have noticed better battery management and even brighter screen in daily use and practice (??? strange, but that's the impression I have). You can find all the improvements of the update here for anyone who wants more information (scroll down to the MIUI 12.5 Changelog section):
https://en.gizchina.it/2021/09/miui-12-5-global-eea-stabile-xiaomi-redmi-download/
Edit 15/10/2021
Now it supports 5G in many parts of Thessaloniki. This particular phone has incredible interoperability and connectivity, as the mobile network card synchronizes instantly with the available 5G networks. The speeds in the area reach 0.5 Gbps (see image), and at this transmission rate, various smart services and applications such as FHD video calls that take advantage of the high bandwidth provide the maximum possible quality in terms of image and sound. And we haven't seen anything yet. Note that the phone didn't heat up at all with the use of 5G.
Edit 13/11/2021
I'm glad that 300 people who voted were helped in their purchase. Health to everyone!!