The fact is that almost everyone in my professional world uses Office, and what I write must be completely compatible with what they use in order to be able to read it.
I am in the same situation - most of my contacts, clients, and associates also use office and most are using windows so being able to "send and receive" documents and "edit and return them" with out complicating things for them is very important for me. Having Microsoft Office is a critical software and well worth the investment - probably the most important software that I have on my working Mac's
One area where Apple shines is Keynote vs PowerPoint - Keynote is far superior (IMHO) and can easily export to PowerPoint if need be, and much nicer to use in a live Presentation. I also use Keynote like a simple "desktop publisher" to create documents especially when graphics are needed - very easy to use and export to PDF or other formats.
One Area Lacking for us "Mac Office Users" is a Data Base software like Microsoft Access that comes with the windows version - of course there is "Filemaker" a very expensive option for most Mac users.