Microsoft are investing in a converter that will allow their customers to read and write documents in the OpenOffice format. This is a good thing. It means if I choose to save my documents in OpenOffice format then I have a choice of two office suites to open them in (three if you count StarOffice).
NB My advice would therefore be to adopt the OpenOffice format to save your documents, whatever software you use to edit them.
Why are they doing this? Well, you will note they are not investing in a Microsoft Office converter for OpenOffice. That would simply encourage people to switch away from their product. I'm sure Novell are already working on such a converter for exactly that reason.
An OpenOffice converter allows them to retain their market share by (i) enabling their customers to open all documents, (ii) pacifying organisations like the Commonwealth of Massachusetts who don't want their documents tied up in a proprietary format and (iii) looking like good citizens.
They could have been really cynical and only funded the part of the project that converts from OpenOffice to Microsoft Office, and not the other way round, but that would have made them look bad. This is the next best option for them.
They may be doing this for slightly the wrong reasons but no matter, it brings their product back into consideration for me. Now the only decision is whether the usability advantage of Office 2007 is worth the big bucks you have to pay for it.