The downside is that if you ever want to reinstall a prior version (such as to view a tax file or look at your worksheets and supporting information), Turbotax versions more than 3 years old are not supported. Your install from CD would be the pre-season version, without the final forms, and no updates or state modules will be available for download. Before deleting older versions of the program, you may want to open your tax file, and either print or save to PDF, "all forms and worksheets", so you can review the detail worksheets later if needed.
