excellent idea, poor implementation.
In general, it is pretty much as I imagined the ideal chair, which is why I chose it.
The positive is that it is indeed very comfortable, it doesn't lock you into a specific position for hours like bucket seats do but gives you freedom of movement, doesn't put pressure on your legs in the center of the seat, has proper lumbar support, and perhaps the best head support I've seen and tried so far (although I would have liked the headrest to be just a bit bigger) without needing the extra cushion that some others have, and in the summer your back and... your butt won't burn from the heat nor will you or the chair stink of sweat.
Additionally, the seat adjusts forward-backward and the backrest up-down, so no one will have trouble finding exactly the settings that suit them best.
Also, assembly was super easy, I only read the instructions at the end out of curiosity and to make sure I hadn't forgotten anything; anyone who has assembled another chair in the past will have no trouble with this one.

And now let's get to the build quality.

During assembly, I had a problem with one of the three screws that connect the backrest to the seat. The screw seems to have damaged (or hit) threads, resulting in it screwing in crookedly and presenting a lot of resistance, regardless of which of the three holes it was tried in. I didn't insist too much, because there was a risk of ruining the chair's threading, so I only screwed in the other two for now and will go to a hardware store to get a regular screw for 10 cents.
For Anda seat, the cost to check the screws they provide with such overpriced products, or at least to put an extra spare screw in the box, would be practically zero, not only for cases like mine, but someone might lose a screw during assembly! But obviously their priority is to cut costs everywhere and not the end customer.

The headrest is good, but it doesn't stay where you leave it since with the slightest pressure from your head it falls or changes position, the mechanism that holds it does have screws, but no matter how much I tightened them, nothing changed.
In general, the headrest mechanism has some play and moves as if it's loose, but it's not the loose screws' fault, it's that the whole thing is made of cheap plastic and they've put more emphasis on the look and design to make the chair look flashy rather than on the practical aspect of making a headrest that actually stays where you put it.

The backrest also has play, looseness left-right, and a bit of creaking from day one, which isn't particularly bothersome unless it gets worse in the coming months due to this looseness and the friction between the backrest and the seat, so we'll see...

The armrests are indeed a great idea, they would be perfect and very convenient in many different scenarios, as they adjust in height, rotate, move forward-backward, etc., if only their construction wasn't so cheap and they had a screw or at least some other way to make them tighter so they wouldn't spin with the slightest movement or weight when you touch them.
In general, don't trust the armrests for anything, if you put your elbow on them a bit more than they can handle, they'll twist, open up, and generally won't stay where you want them.
They're there not to support you but just to barely rest your elbow so your wrist can reach, for example, the desk.
Especially those of you who are used to or need to support yourselves somewhere (most people who need an ergonomic seat and not a flashy bucket after all) to get up from the seat, get ready for many comical-tragic moments and a lot of cursing...

In general, the manufacturer seems to have fallen out with quality control and is selling seats at overpriced rates based solely on the logo they put on the headrest.

My advice: don't buy it unless you see it up close and try it first to see if it suits you!
For the 100-150€ category it would be fine and I'd probably give it a higher rating, but for a cost of 350+ it's poorly made and overrated.

First of all, let me say that I have a herniated disc in my lower back which had left me bedridden for a month. I work an office job for 8 hours a day and generally sit at the PC for gaming, etc.

I bought the chair because I was going to work from home for 3 months and wanted to replace the ancient chair I had. My partner has the Anda Seat Kaiser II. I was thinking of getting that one as it is a pretty good chair, well-built and comfortable, but it is definitely not for someone who has a serious back problem.

I decided to get this one as all ergonomic chairs are expensive, there was no consistency in recommendations for a chair ideal for back problems, as it is something very personalized for each person. I couldn't find a reliable brand, and the Henry Miller ones are €1000+, which I can't afford. I've had this chair for 4 months now. I can say that it's ok. Easy to assemble, very cool for summer, nothing like the Anda I mentioned above. It's lightweight, the armrests have 2 positions depending on the size of the person sitting, the headrest moves up and down and the "pillow" has positions it can go to, the backrest moves up and down in several positions and the armrests go up and down and also tilt right and left. The chair has a good recline if you want and locks in several positions. From the start, there was a creaking sound in the backrest, and the backrest has a wobble, something I had seen in reviews I checked before buying from other buyers.

Now, regarding comfort with my problem. I am quite comfortable. It keeps me stable and straight. After discussing it with my physiotherapist and showing it to him, he told me it seems good. It takes a little time to get used to, and it's not like you sit and say wow, but it's comfortable enough to keep you stable and not hurt in the long run.

The quality is ok. The backrest is full plastic, which I don't love. The mesh of the chair hasn't suffered any damage so far, but I definitely don't recommend using it with jeans or anything that could tear the mesh, because I think it's easy to damage. It's a nice-looking chair and easy to clean from dust. I don't recommend the more expensive model, I saw that the differences are very few for about €100 more.

If someone wants a budget ergonomic chair, I recommend it because it's a known brand compared to other budget options, it has a warranty, it's good-looking, comfortable, and cool in the summer. It's not something amazing as a chair, but it does the job it should. If someone has a serious problem and has the money, they should get a Henry Miller or discuss with a physiotherapist what chair to get based on their problem.

POSITIVES: For an ergonomic chair, I would say its price is relatively cheap. I bought it first before a month, just in case they raise the price, as good ergonomic chairs usually start from 500-600.

Now, on to the essence, I had the Anda Seat T Pro 2 for 4 years, which of course didn't suffer the slightest damage all those years and I still have it, but since last year I realized that something was wrong with my back and knees after a few hours on the computer, I started thinking maybe I should switch to an office chair. In the end, I was right, and that was the issue. Now everything is correct, and I can sit normally for 3-4 hours at the PC without the pains and discomfort I had with a gaming chair.

EDIT: NEGATIVES, I am coming back since I see the interest of people in my comment. After 2 months of use, I would like to mention the small negatives: 1: The back of the chair has what is called a WOOBLE, meaning only the back moves as if it hasn't been screwed in properly. I took it apart, put it back together, and saw the same thing again (since the first day). I called the company, they asked for an email with the problem, I sent 2 videos, and they told me from the company that it is absolutely logical, and because it is ergonomic, that's how the chair should be. Personally, it doesn't bother me particularly, and it may indeed be logical.

The second problem, which is a bit more significant, is that the back and lumbar support do not come very close to the lower back. For an ergonomic chair, I expected it to keep my back completely straight, but that doesn't happen here. You are forced, even if just a little, to lean your back slightly forward when you are focused on some work or gaming. Of course, this is my first ergonomic/office chair, and there may be a reason for this, and it could happen even in the more expensive ones out there! I don't know!

In the end, I do not regret the purchase. The fact that I can now sit for 5 consecutive hours without pain anywhere is the most important thing for me. For some reason, my knees also hurt in a gaming chair, but that doesn't happen here. With the gaming chair, discomfort would start after 40 minutes, and I had to change positions.

Be careful, there are 2 versions of the chair; get the more expensive one (the one I am commenting on here) because the difference, if I remember correctly, is that the seat moves back and forth, while in the cheaper version, the only difference is that. That's also why my knees don't hurt, because you can adjust it so that they don't hang or the opposite. Personally, I have the seat all the way back and the backrest all the way forward. (1.79 height - 75 kg)

Also, the headrest of the chair is useless to me; you will only need it when you recline the chair back.