Brian Jones is a PM for Office, concerned wth the XML formats. His article gives relevant information.
One comment there says why it is important to have this support:
Excellent resource! This tool will now allow developers easy access to those Open XML Formats in Office 2007. Finally, all developers can easily retrieve, store, and use all those office files that have been sitting on their servers and directories all over the place but have been difficult to use in applications, etc. etc. The combination of Open XML Formats in Office 2007 along with tools like Altova's XMLSpy or MapForce is like finding the pot of gold at the end of the rainbow! Thanks to Microsoft & Altova!
(BTW this plain text message board is a bit hard to take. I thought typewriters became extinct a decade ago).