There is really only one reason to hang on to Office: Excel. There is a lot of development that has gone into add-ons that can really enhance its analysis capabilities, especially in the areas of:
- Monte Carlo simulation (either with hefty price tags with Oracle's Crystal Ball, or free with SimulAr, but others exist as well),
- heavy-duty mathematical analysis with R through RExcel, and
- visual presentation (such as through Fabrice Rimlinger's Sparklines for Excel).
Check out Apache OpenOffice and LibreOffice. While functionally the same,the latter currently has a slight edge with respect to import/export filters and a wider selection of extensions to enhance its capabilities, as well as a development roadmap that is slightly ahead of Apache's. They are both worth exploring, and many large organizations have already undertaken migration in that direction. There are also ways to use the analytical tools I have mentioned above as separate steps in the workflow (as opposed to full integration), but I have not been able to find a suitable sparkline alternative for this platform.
Try it. I'm sure you will be pleasantly surprised.