I just got my MBP and decide to try iWork instead of office so here is my experience.
I am a teacher and taking college classes as well so I use office daily (no exaggeration). I liked the price of iWork and I think I like keynote over powerpoint so this is why I purchased it. I started my testing of pages with word documents that have special formating and it just destroyed the formating. THis is a problem because I need to share documents with co-workers at times and they might have an issue if they don't know what they are doing. You can play around and try to get your formating back but it is a waste of time. Just one example was making a document in pages in landscape mode, saving it as a word file then opening it in word set the formating back to the normal view making it look crazy.
I would say if you will never share a paper or do any kind of special formating (unlikely in your situation) then iWork is totally fine for you. I can't use iWork only but I spent the $41 on keynote and I think you really should get office-I doubt you would regret it.
Also, Apple and Microsoft allow you to try their programs for free for 30 days so just download the two and play around with them.
Maybe others could talk more about using the two.