I use OpenOffice. While there are some quirks (as there are in most packages) I have yet to see a reason to use anything else. To me the only reason to use Office is if you need Outlook. Word Processors and Spreadsheet stuff can be handled by other applications.
Also you might want to keep tabs on OpenOffice.org, it seems that Oracle (Acquired in the Sun purchase) has not been providing the support they promised and a spin off has occurred with a large portion of the developers moving to the new organization.
LibreOffice is the new app and a new Foundation was set.
Welcome to The Document Foundation! - The Document Foundation