First of all, let's get this out of the way - we love height adjustable desks!
They work perfectly with Salli saddle chairs, but if you believe the hype then you would be convinced that sitting is evil - it isn't.
Many health problems are related to being sedentary, while many musculoskeletal disorders (MSDs) are caused by the very "ergonomic" chair that many sit-stand desk users continue to use (you can still have back, shoulder and neck pain with your sit-stand desk!).
Put simply, sitting is not the new smoking (see this article which offers a real comparison without the hysteria).
(note the different sitting postures with the same desk, different chair)
This is a scare tactic marketing phrase, and has worked brilliantly. A huge percentage of office based workers (many using traditional "ergonomic" chairs by the way), have jumped on the sit-stand bandwagon, most not quite achieving the magical results to back, shoulder and neck pain as promised.
Considering most people will still be sitting for 80% of their work day (in many cases 100%!), the benefits are overblown. Standing too much isn't good for you anyway. In the rush to promote these desks the downsides to standing are not well promoted.
The fact is that, as a general rule we are creatures of habit. If we find it comfortable to sit on our regular "ergonomic" office chair - then we will mostly sit, even if it is gradually doing us damage. Saddle chairs with sit-stand desks are ideal as they provide a way to sit, but also provide a physical intervention which does not require thought.
Once you have a saddle chair and get used to it you will not have to think about sitting healthily - you will just do it - and you will be maintaining a neutral, standing posture - which is the key ingredient to preventing many MSDs!
Do you think all those workers on their feet all day want to sit down? You bet! It is natural to want to sit and take a load off your feet.
Check out these links for some different, alternative views and experiences with standing and sit-stand desks.
Ideally you will be mixing movement, standing comfortably, and sitting on a healthy chair such as a Salli Swayfit ergonomic saddle chair which has active sitting.