The Excel 2007 filter for Calc is still on its way, but perhaps now is a good time to show the progress of this new Excel 2007 import filter work by Daniel Rentz and myself.
Here is a screenshot of a file created by Excel 2007 (left), and one for the same file opened in Calc (right).
There are still a lot to be done, however. Formula import is still to be completed, which blocks other features that rely on the formula parser. Charts, text boxes, and other graphic objects are still not imported yet. There is also a performance issue of a large xlsx file import, which needs to be addressed at some point.
But all in all, things are coming along very nicely.