ISS has made a lot of progress on learning and ameliorating the effects of 0g on humans. It's only about this year that techniques to control bone loss over the

ISS has made a lot of progress on learning and ameliorating the effects of 0g on humans. It's only about this year that techniques to control bone loss over the long term have gotten really good. Astronauts can now routinely return after six months not crippled, which is a huge advance on the state of knowledge circa Mir. Yes, most of the science on ISS is human science, related to 0g, and it is pretty expensive, but there's not much other way to do it. I'm not sure that 0g habitation has a long-term future (it's still not very good for you) but we wouldn't really know that without the ISS. It also hosts plenty of materials science and remote sensing experiments along with the biology and space medicine. It's a weird environment that we're only just beginning to figure out.