I work on the floor, with my back against a couch. I have a computer in front of me on a coffee table. Whilst working on the floor I will do things like the splits, and various other yoga-like postures.
I am doing this for about 40 hrs a week. Do you think this is better than sitting on a chair? I change my postures regularly and do extra stretching throughout the day, whilst still sitting.
It seems comfortable as you describe. The first things I'd check is that:
Having said that, I assume you're frequently typing, not just watching the screen. Ideally there'd be a keyboard located just above your legs, like on a home-made step or by setting up some yoga blocks between or alongside your legs, to set the keyboard down on. Then the monitor or laptop screen placed on the coffee table so that most of the time you can simply look straight toward it without tilting your head up or down. If it tilts down a bit at times, I suggest a tucked-chin position to keep the weight of the head from dangling forward at those times.
My expertise on this matter is from 4+ years as a fitness trainer dealing with all sorts of posture problems. One rule of thumb I have: if you can feel the weight of your head while you're working (or watching TV), or there's any feeling of muscles active in your back, some portion of your body may not be aligned well at the moment so adjust as needed.
