Great ergonomic chair for working in all day. 
The arm rests are very adjustable and I'm able to set it just at the right height and position for myself. The horizontal adjustments are especially useful. 
The lumbar support is not adjustable, however, it has a spring to it so it move if I sit fully back into the chair and is extremely comfortable. 
I was unsure about the headrest before making this purchase, however it does tilt and it's been kind of nice when I do lean back. 
Assembly was easy, about 30m with unpacking and cleanup.
The reason I gave this 4 stars instead of a 5 is because 1 week of daily use and it squeaks when I lean back. In addition the wheels are smaller than my old chair and does not role as smoothly on my chair mat. I'd give it a 4.5 if I could.  

Overall, I recommend this chair.