Sitting, Standing, or Lay-Down Desk?

I have just moved into a new place. The ceilings are pure white, I have a sleeping pad for a mattress, and am tempted to setup a "lay down desk" of sorts.

I picture myself laying down on the mattress, with my desktop projected onto the ceiling above me, a mouse sitting on the ground, and a wireless keyboard on my lap.

Would this be "better for you" than sitting down at a desk, do you think? How about compared to a standing desk?