Having never used an observers chair before, it took me a while to work out how to use it properly. It is light, compact and practical, though its more challenging to use on uneven, sloping ground. The manual instructions are minimal and can be interpreted in more than one way, which as I found out, can lead to using an incorrect method to adjust the seat height. Berlebach's responses to my query about adjusting the seat height were not exactly helpful, and the two video links they provided were of little benefit.
For novices like me, I would say care is needed with the seat at very low levels, as the chair can easily tip forwards. Its perfectly manageable, but its good to be aware of the issue.
In summary, I'm very pleased with this chair, and it would merit 5 stars if better information was provided by Berlebach.

I've had observing chairs before. They've been heavy or they've had springs and things and, to be honest, they have got in the way of my observing pleasure; the Hydra II improves it. It's light, compact in use and for storage and, in my opinion, comfortable. The other big plus is ease and range of height adjustment. I've long been a fan of Berlebach tripods but I wish I had taken the plunge with their observing chairs years ago.

Like others, I did wonder if I should spend £200 on a chair or buy an eyepiece. I have to say, I’m glad I bought the chair. It is a very simple design and very well made with quality materials. Sometimes things just feel right and this chair does. It is comfortable, easy to adjust and just about the right size. I don’t really have any negatives, just the fact that it’s expensive but then there’s a certain satisfaction in owning something that gives you pleasure even when you are not using it.