Last week the newest version of OpenOffice was announced, and the new release revived the discussion whether or not OpenOffice is better than Microsoft Office. Although I don't particularly like Microsoft and normally don't care about office suites, this latest release did get me thinking.
How about export to PDF, and being able to define new functionality with Python? OpenOffice is even usable from a script, so it can be used to do things like programmatic document conversion. None of the others mentioned do that.
It's free. It does most of what most people need from an office suite. It does not require being online. It runs on all the common platforms. I think that pretty much sums it up.