Quoting Kim Hyatt <kimharch@cut.net>:
My memory is far from perfect, but I can't recall a single bit of science being reported that was grounded in experiments done aboard the ISS. Anyone?
If we plan on establishing a permanent base station on the Moon, or if we plan on travelling beyond the Moon to distant planets, we will need to know just what medical effects long term exposure to zero gravity will have on the human body. I think ISS provides a great and necessarty platform for that research, as well as providing a living environment that could be used as a model for living quarters once on the Moon. If you're going to live on the Moon or travel long distances you are going to need to know how long certain supplies last, how well your toilets function, how to provide water, how to make your air supply last longer, all kinds of things that the ISS does on a daily basis. You need to know how humans can coexist for extended stays in otherwise cramped quarters. A whole host of things that can't be done on Earth. So I think the ISS, in a not so glamorous way, is a great platform for the study of the things that NASA will need to know to advance space travel. But I could be wrong...