Users can now export Google Docs files in OXML formats (.docx, .xlsx, .pptx). This will show up as an option in the “Download as” menu.

Editions included:
Google Apps, Google Apps for Business, Government and Education

Note:
Rapid release domains no longer have the option to export files as .doc, .xls or .ppt.

For more information:
http://support.google.com/docs/bin/answer.py?hl=en&answer=49115

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