Based on your responses and comments on this thread i'm inclined to think you're a fairly logical decision maker. You obviously have a need for a new computer or you wouldn't be posting in this forum and asking these questions. It would seem logical that you also have a working computer that can do most everything you need. If you didn't you would be less willing to push off your purchase to late October... Now consider the opportunity cost of your time as part of your purchase decision. How much more productive will you be with your new machine and office vs your current setup? Do you think between now and November that you might accomplish 4 more hours worth of work because of your new setup? If you make 50K a year or $25/hr then you should consider spending that $100 to get office and the mac now. The marginal increase in your productivity justifies the purchase sooner than later.
Plus if you go to amazon.com you can buy the Business version of office mac for $
244 and then you only have to justify $44 dollars over 3 months.
I've tried and didn't like both openoffice and iwork. I found that I spent too much time figuring out formatting and excel commands. They both have their place but they cost me too much time to be used on my personal work machine. This was two years ago so much has probably changed.
Just my two cents. Hope this helps your decision.