Over the course of five years, we've had approximately 40+ windows in our home replaced by Colorado Window Source. They took out all of the old wood windows and put in new windows for us and the quality of their service is good. They aren't just slapping the windows in, they make sure all of the windows fit and if they catch a problem while installing the windows, they'll make sure to fix it before they leave so they won't have to come back.
Their prices are comparable and the quality of their work is excellent. I'm a highly satisfied customer and will use them again in the future.