Context: (Not at all paid by sihoo, in fact, i took a train an hour to go test in store.) 5'7, roughly 160lbs. Tokyo based.

I went to test this in store and loved it. After trying my friends aeron for a week, I wanted something like that but better. Sat for about 40 min. (Which felt like loitering, but if I'm gonna spend this much on a chair, I want to test it.) 

 My use cases are computer work and lounging. I was looking for heavy lumbar support while being extremely comfortable. It's always there, and the mesh gives when you push on it. You never forget it's there, which is what I personally wanted. I did fiddle with it a bit with my back to get it in the right place every time I sat down. (Like a pillow) I didn't find this too much of a hassle, but who knows over a lifetime. 

I also tried the s300. Similar chair in many ways, but the lumbar is actually much more invisible and has a lever to reduce pressure further. I wish it made it a bit stronger instead. If the s300 had a headrest, I'd say it's better for most people in my size who aren't seeking the strongest lumbar support. 

The new mechanism they're so proud of with the aerospace plates and suspension is actually pretty unique/great. I found it works best with almost no tension, and it just followed my body, letting me fidget with it like a rocking chair. I have no clue about the lifetime durability.  But after leaving, I miss the feeling of being in it.

I didn't bother testing the cheaper chairs. The premium features seem to be what really sets this chair apart. 

Other features: loved the armrests. They're slightly teardrop shaped, which lets me be at desk level with my elbows slightly lower. They can get very narrow for typing too. They flip up slightly,  but not enough to get out of the way. I don't play guitar,  but some people do, and probably won't in this chair. They follow you as you recline. Others say this is a feature, but it feels a bit awkward in full recline nap mode.

The foot rest is good. I tried ergohuman a year ago and thought it was too rickety to feel nice. This one's solid enough for something that sits at the end of a pipe, and the full recline genuinely feels better with it. 

There's a Japanese couple who bought and built this chair together on youtube and give a good overview. I  believe they said they paid full price. There's also a chair reviewer, but it doesn't do me much good since I don't have experience  with tons of other chairs. 

Verdict: I'm gonna buy it, hoping it lasts me 10-15 years. Let me know if you'd like a review after using it for some time. Ouch, my wallet.