Our newly furnished balcony has quickly become my favourite "room" in the house. If the weather allows I'm spending most of my time here. It has only been a few weeks and I think I have spent more time during this short period of time than all the other times during the six years we have lived here combined. Definitely a good investment. With a few hundred euros we got an extra 12 square meters room.
Of course there are some limitations and challenges on it's usage. Weather being the biggest one. It won't be that comfortable when it's cold and raining. The sunny weather isn't without problems either. It can get hot in here and the brightness hinders any hope of using any screen devices. Which isn't necessarily a bad thing anyway. And it can be easily fixed installing some shaders to block the excess sunlight.
Sure it doesn't raise my activity levels much. The couch is just a few more steps away from the fridge. But at least there is fresh air and natural light.