Binos,
Glad you're enjoying the iMac. As far as I know, the Standard Edition of Microsoft Office allows you to install it on both laptop and desktop. However, it doesn't allow you to run both at a time. If you have purchased the Student/Teacher Edition, there are three licences with it. However, it isn't upgradeable. Office works fine on an iBook, and is almost standard-issue for most consumers and students. If you don't need a spreadsheet, iWork offers better value and is far easier to use, of course.
Apple have yet to release details about any new "consumer level" laptop, currently occupied by the iBook G4. The MacBookPro is aimed at a professionals, and has a higher-end specification, hence the price.
AppleMacster