Well, the responses haven't been so forthcoming so I decided to do a little digging myself. Here is what I've managed to gather, in a nutshell:

Kneeling chairs were originally invented with the aim of improving lumbar curvature and reducing lower back pain, claims backed by several studies, although it has to be said research into the area is mixed: https://en.wikipedia.org/wiki/Kneeling_chair
They offer a few benefits, most importantly being that individuals suffering from back pain can benefit from using kneeling chairs - or anyone looking to improve their posture in general: http://ergonomictrends.c...benefits-pros-and-cons/.

Their awkward design might not suggest so, and you could be forgiven for thinking otherwise. Because apparently, this design has its own caveats, although not so much on the spine (good news) as on the legs (read shins). For example, the pressure exerted on the shins can not only prove uncomfortable in the short term, but may result in pain over time.

And of course, there is the small matter of lumbar support, although this is negated by the fact that kneeling chairs come in many shapes and forms: https://chairinstitute.c...pes-of-kneeling-chairs/. Personally, I think I would prefer a model with back support, so this would likely feature highly on my desired features should I decide to explore them.

But the general consensus is that kneeling chairs alone are not an elixir - neither is any chair, yoga ball, or standing desk. The trick is to vary the posture by alternating between kneeling/sitting/standing/moving about as staying in any one position for prolonged periods is not ideal: https://www.medicalnewst....com/articles/321863.php

Fan fact: Apparently the concept of kneeling chairs has been around since as far back as 1979 and was the brainchild of three Norwegian designers. They also go by the fancy name of balans chairs.