As time goes on things change, and this is the same for software as well. A while back one of my favorite pieces of software, Open Office, was taken over by Oracle. In case you unfamiliar with Open Office, it is basically an open source office suite that is compatible with many formats, including Microsoft Office. Some of the developers of Open Office broke out on their own and created their own product, called LibreOffice.
LibreOffice looks very much like Open Office, except it has a lot more compatibility with Microsoft Office 2007 file formats. This to me is very significant since I am working with them more and more. In the past however Open Office was able to work with Microsoft Office 2007 documents just fine, but there is more stability with the new LibreOffice. There are also several other enhanced functions, but I have not done anything so advanced to use them.
So why the change? I was very happy with Open Office for quite a while, but I had some of my friends that told me to switch for some of the Microsoft Office compatibilities. What really sealed the deal for me though was, when Ubuntu Linux 11.04 came out, it came with LibreOffice and not Open Office. This is probably for the fact that the developers are keeping LibreOffice open source, while the plans for Open Office with Oracle are still being decided.
So if you are looking for a free, open source office suite. Or are an Open Office user looking for some extra compatibility, I would give LibreOffice a try.