Go ahead and laugh. I have MSOfficeXP at work and even with the compatibility pack installed, it won't open many files I get that have been made on newer versions of MSOffice. Open Office does not have this issue.
I’m a big, big, MS fan, running Win7 on an intel build.
Even I run OO, exclusively. As for the MS formatting, it’s easy enough to fix it so that the MS formatting works well in both OO and MS.
Now that being said, OO, has some very BIG BUGS that have cost me considerable time and money. One of them being the old bug with their restore. Restore won’t retrieve autosaves, as I found out the hard way. That’s since been fixed.