I've recently discovered salli chairs for myself; I found these chairs to be OK for a stack sitting, but what is about stretch sitting? Is that OK not to be able to stretch sit for the whole day???
Any other issues the chairs may have?
This is a saddle stool. These can be comfortable and conducive to stacksitting, whcih is good. I don't consider this quite a chair. It's a good stool to perch on, but depending on your back you may want to have an additional arrangment to get you some back traction in your day. Most people have some degree of compression in their spines - in this case it is very useful to spend some sitting time in traction (stretchsitting).