as an ex owner of Markus:
1. the lumbar support isnt adjustable, so it's not one size fits all
2. headrest is too tall for certain people, and it's tilted at an odd angle
3. the arm rest is fixed, too wide and too low for certain application, also the way it's assembled doesnt allow you to sit cross legged, if you fancy that kind of posture
4. seat cushion depth isnt adjustable so those who're short wont feel comfortable wtihout a footrest
5. the backrest frame is stiff, it doesnt allow much micromovement on the shoulder blade

other than that it's actually quite comfortable to sit in