I use Office for assignments and iWork for more personalised documents (such as CVs, invitations, etc). Thing is, as much as I'd like to use Pages over Word, I feel much more comfortable in the blandness of Word to make a simple, black and white, double-spaced printout for submission.
Again, as much as I'd love to use Keynote for all its much better effects, smoother transitions and speedier performance, a great deal of the bells and whistles are lost when you try and play a Keynote exported .ppt file on Office. Ultimately, it becomes a waste of time. There is also the addition of the unnecessary risk that it might all fall apart, and believe you me, that's the last thing you want when you're trying to focus your attention on giving a kick-ass presentation when leading a seminar.
Sadly, Numbers is nowhere near what I need for my spreadsheet work either. Whilst I don't claim to do anything blindingly difficult (I do statistical analysis for business and management alongside my economics and politics degree) the ability to be able to write, simple, effective VB and VBA macros that can give you reams of useful information on a massive series of numbers within a few seconds is a godsend. Whilst Excel for Mac is a garbage version of the Windows one, working with a Windows Excel file with Excel on a Mac is much easier than working with it in Numbers on a Mac.
Office is a crime of convenience. It's r-tard easy to use, it will be the standard issue on your campus, and it's dirt cheap to get through either your institution or Microsoft themselves, via
http://www.theultimatesteal.com.