The Mac version of OpenOffice currently requires X11 to run, which is not properly integrated into the OS X look and feel and to all accounts doesn't look too good. There's NeoOffice, a port of OpenOffice which does run natively under OS X, but I've heard there will be an official OS X port of OpenOffice coming out quite soon.
OpenOffice is largely (though not 100%) compatible with Microsoft Office documents, such as Word and Excel, though you'd have to convert any macros you might run.
Anyway, they're both free, so you've got nothing to lose but your time!
(Took the links out as they may be construed as advertising. JFGI!)
Last edited by Dop; 8th September 2006 at 10:59.
Reason: thought original links may be construed as advertising!