I missed this last week: http://blogs.sun.com/GullFOSS/entry/office_open_xml_import_filter

It looks like some folks in Sun are working on support for Ecma 376's SpreadsheetML format within Open Office:

The development of a new spreadsheet import filter has been started in the Calc project. This filter will be able to read the Office Open XML file format for spreadsheets introduced in Microsoft Office 2007. The filter is already able to load simple cell contents (strings and numbers). Currently I am working on cell styles and cell formatting…

This is very cool. There are some other spreadsheet tools out there already that have varying levels of Open XML support, and it's cool to see that Sun is working on adding this into OpenOffice. Some of the folks from Novell who were on Ecma TC45 work directly on the OpenOffice source, but I'm not sure how much they are directly involved with this latest project.