It can be used for reading. I agree.
Writing coursework - do you really want to write more than a couple of lines of text on a device that doesn't have a physical keyboard? (you cannot rest your fingers on the screen without causing "touch") Same argument works for taking notes. I cannot possibly imagine working with a spreadsheet or graphs on the iPad.
Sharing information - you cannot run more than one non-stock application at once. I expect it's hard to share anything in that kind of environment.
Communicating with others - by default you're left with IM. Unless you buy an additional Apple-approved camera (cheapest laptops include webcams these days).
Doing any proper research - that needs at least a browser and text editor running at the same time. (unless you take notes on paper)
There are additional keyboards of course, cameras, etc. but why bother? Any half-decent netbook is much better suited for learning purposes than iPad. I can understand not being able to spend $6k on a laptop. Not sure what the situation is like in US, but in UK you can get both 3G dongle and laptop on a 2 year contract for £35/mth. That's just above $1k spread over 2 years (with internet included). Are we talking about education, or are we talking about expensive toys?