Going back to the question about office or iWork's, unless you have some compulsive requiment or a huge number of office document I don't really see the advantage over iWork's
As a personal and VERY light business user I find iWork's fulfills all my needs, pages and numbers are pretty good, but I never use keynote. There are other cheap option too such as open office.
On the new iMac front, it's worth remembering that the new 21" has NO user RAM upgrade, what you buy is what your stuck with. the 27" has user upgradedable RAM though.