Office 2007 was a pretty specific case where MS gave people an opportunity. The UI hasn't changed that much since Office for Windows arrived and it won't be repeated for at least a decade, probably more.
As an aside, the interesting thing is once people get their heads round the UI they pretty much universally like it, it's just the instant reaction that's so bad.
I did try OpenOffice for a month (pre-Office 20070 and you're right, it's horrible.
But even if it was functionally equivalent there are still reasons Office wins - because it's safe and because it's the defacto standard.
Even the cost isn't that big a deal for companies because they get security in exchange and that's one of the things big companies value above all else.
As an aside, the interesting thing is once people get their heads round the UI they pretty much universally like it, it's just the instant reaction that's so bad.