A bean bag couch is probably the most comfortable couch or seating arrangement you can find. The small beans are made of styrofoam peanuts or polystyrene beads.
There are as you probably know, more than a dozen brands on the markets, offering bean bag chairs, couches, love seats etc.
One of the best bean bags you can find is the Fat boy. It is very resistant against rips and tears. But with the high quality comes a high price too.
The downsides of a bean bag is that it can be pretty hot after a while, at least if it’s made out of a synthetic material, not much air will get through and the beans acts as an insulation. The posture that you end up in can be discussed too if that’s the most ergonomic.