I'm in the same situation, probably more so, since I have an 11" MBA.
But for me, I sold my original iPad to fund the MBA, which at the time was the best thing I could do to make my workflow better. However, I do miss the iPad for really fast browsing and consumption stuff without having to pull out my laptop. In between classes, walking around campus...places where having a laptop out is just awkward to do/hold, the iPad is unbeatable for that.
As for the school work part, I would probably only really use it for research browsing and stuff like that. Although, I did create a sweet Keynote presentation on my iPhone last semester that destroyed everyone else in the class, but maybe that was because none of them seemed to know how to make one. Keynote, Pages, and Numbers are all well done on the iOS devices for most tasks. It's just more advanced stuff is where a computer will be needed.
If I have the money when iPad 3 comes out, I'll be getting it. 😀