I recently had the opportunity to download, install, and use LibreOffice. LibreOffice is a free suite of office productivity software from The Document Foundation. The most recent version of it is 4.3.1.
Upon installing LibreOffice, I noticed that its user interface was almost identical to OpenOffice, which had used before, with one exception: the icons and buttons had a more modern, fresh look to them. This was not the reason I downloaded LibreOffice, however. Actually, I downloaded LibreOffice because I had read on Wikipedia that it allowed the editing of the .xlsx format.
Long story short, for some work I was doing, I needed to be able to edit a colleague's .xlsx file using my desktop computer and, after attempting to do so, I found out that OpenOffice Calc simply cannot allow one to edit a .xlsx file. I found this odd because OpenOffice Calc does allow one to edit a .docx file. (The x at the end of the file extension indicates that the file is in the newer Microsoft Office XML file format.) Moreover, I have had no problems using OpenOffice to open and edit .doc and .xls files. (My desktop computer does not have Microsoft Office installed.)
Well, it was late at night and rather than bug the colleague to re-save the file into the older .xls file format and send it back to me, I decided to do a little research online. I found LibreOffice and like I mentioned earlier, I downloaded it. I gave it a try and voila--it worked! I was able to open, edit, and save the .xlsx file with no problems. Because LibreOffice is able to do this, and it also does almost everything that OpenOffice can do, I now use LibreOffice instead of OpenOffice on a daily basis. Also, I still occasionally use Microsoft Office on my laptop when I need to run, for example, Visual Basic for Applications (VBA) macros.