I'm a student and have been very happy with the NeoOffice and iWork combination I use.
For the longest time I used iWork alone and was very happy with it, but there was an occasional formatting error converting tables and the like into word. Also, I missed having a built-in thesaurus. (I know I can use the system one, but I hate having to cut and paste the words into the document instead of having a replace button) Usually if I wrote a huge document with a lot of formating, I would have to carefully proofread it after converting to Word.
Since then, I have discovered NeoOffice though, and the compatibility is spot on. The docs aren't as pretty as if I were using iWork, but when working with groups this isn't really that important.
Too be honest, unless there is some killer feature I don't know about, I can't see myself plunking down the money for MS Office at all anymore. The only need for it is to entice switchers who feel that they somehow must have MS Offce to survive. For seasoned Mac users though, I imagine most of us are smart enough to know that we can do 95% of everything MS Office does with NeoOffice, iWork, or LaTEX.
IMO, it is very fishy that the level of support that MS gives to the Mac platform is dwindling as Macintosh market share increases. We no longer have a MS developed Windows Media Player, the MSN client is a joke, and I imagine Office 2008, when released, will be somehow nerfed as well.
(I tried OpenOffice.org Aqua but found it to be buggy and not ready to be my primary office suit.)
What is that you are doing that you need MS Office for anyway?