I've been using a self-built prototype floor-sitting desk for the last month. I can sit cross-legged, on my heels, or with my legs to one side, as well as squatting.

It's 2 shelves: one about a foot off the ground for the mouse and keyboard and another a little more than a foot above the first for the laptop to sit on. I look directly into the screen.

An improvement would be better adjustability and possibly taller supports so that it could be used while standing as well.

Either way, I'm very happy with sitting on the floor. Now, when I sit in chairs I notice misalignments arising quickly.