iWork,TextEdit,NeoOffice
Neooffice.org is OpenOffice for Mac, and I find it satisfactory. I only use it when I want to open, edit, and return Word files I've received with the maximum preservation of formatting. There's no need to spend money on Office for Mac, or have MS software in your Mac, unless you need some very specialised business and scientific functions which are exclusive to Office. NeoOffice/OpenOffice is a very satisfactory equivalent for most people.
Word documents can be opened very quickly in TextEdit application which is preloaded and which is a lightening quick way of opening, creating and editing documents with basic formatting. TextEdit documents can be saved in Word, RTF, HTML and other formats.
iWork has the kind of advantages over Office that the Mac OS has over Windows. User friendly, aesthetic and logical way of working. Really draws you into creating documents (Pages), presentations (Keynote) and spreadsheets (Numbers) in new and interesting ways. It even makes spreadsheets look really attractive and interesting, and fun to work with, though that's the area where there's the biggest lack in business/scientific functions compared with Office. Pages 'publications' can be easily exported in Word, Pdf, RTF, or Plain Text. Keynote presentations can be exported in PowerPoint, Pdf, Flash, QuickTime, Images, Flash, Html and iPod formats. Numbers spreadsheets can be exported in Excel, Pdf and CSV formats.
I've given up Office after many years and have not missed it at any point. Don't bother with it unless you really do need some of the more specific high level functions. I would not like to be without iWork and I use it intensively.