The answer is that it depends on what program and computer the user is working with. The main question for those users is of course how they would open a docx file to be able to read and work with it. The problem with the change from doc to docx is that many users are still working with older versions of Word or no Microsoft product at all and face the problem that they can't load the docx files because they are not supported in their application.
docx file format in its new Office and Word applications in Office 2007 and wants it to replace the commonly used doc format.
