Sun making progress with OpenXML too ...
according to Sun's Daniel Rentz who posts an update about Sun's "Ongoing Work on Office Open XML FIlters".
Work on the Office Open XML filters is in progress... The spreadsheet filter is now able to load cell contents (except formulas) and most of available cell formatting from XLSX and XLSM files. Next big task will be to implement importing formulas and features related to formulas (defined names, external links, print ranges).
I have built installation sets for various platforms, if you are interested to play with a very first version, browse to http://ooo.services.openoffice.org/pub/OpenOffice.org/cws/upload/ooxml/install/. The childworkspace for this project can be found in EIS: http://eis.services.openoffice.org/EIS2/cws.ShowCWS?Path=SRC680%2Fxmlfilter02.
Interesting that at the same time Sun's marketeers disparage the OpenXML spec its engineers are using it to build interoperability - something others can't do with ODF since
those bits were deliberately left out.