I noticed the other day when I received a document from a client that he had sent it in Word 2007 format (.docx); being on a Mac, I obviously don't have immediate access to Word 2007 and because it's never been an issue before, I didn't even have a converter installed.
However, once I'd copied the document to my downloads folder, Finder spawned a preview icon of it immediately and much to my happy surprise, I was able to not only Quick Look it, I was able to open in it TextEdit and work with. Even better, the app also allowed me to save it in the older Word format with no loss of integrity.

