The Indows seem to fit well, they do stop air leaks and they do dampen outdoor sounds. As far as room temperature control, though, I have to say I don't see a difference. Ours is an old house, the rooms were cold, and they're still cold. Our home insulation is likely so inadequate that it dwarfs the windows' contributions. This uncertainty is an important issue that the company ought to address somehow. Another obvious issue is that for large, double-hung windows, removal, storage and re-installation of the Indows is an awkward and time-consuming process, so that getting some fresh air in the room can become a chore.