A few months back I got a new laptop but due to a hiccup in the IT department of the organisation I work for there was a delay in getting Microsoft Office installed on the machine. The Laptop was no use to me without some Office Program so I installed the latest version of Open Office as a stop-gap for the couple of days it would take to sort out the IT issue.
Here I am three months later still using Open Office version 3.2.1 on the Laptop. It just works and it works well enough for me not to be bothered about replacing it. I use a word processor, spreadsheet and a presentation programme on a daily basis and the Open Office equivalents do everything I need them to do and are just as easy to use as the Microsoft versions. In fact I slightly prefer the default style and menu layout of Open Office Writer while I think Power point still scores slightly in usability over Open Office Impress. Overall its a tie.
Most impressive is the compatibility. A few years back I experimented with an early version of Open Office and abandoned it quickly because of format corruption. Now however after months of use I haven't had a problem opening documents nor have any of my colleagues had a problem reading my documents. I save everything in Office 97-2003 format (*.doc, *.xls, *.ppt) even though OO recommends using their default format instead but it has never given me a problem. To be honest even if I was using Office 2010 I would still have to save in these formats because a surprising number of people still can't read the newer *.docx and *.xlx formats.
I still use Microsoft Office on my desktops but I am strongly considering a complete move to Open Office including using their ODF file format. I particularly like the fact that it would remove any ambiguity over licensing on multiple PCs.