Is it possible? Yes, with an external keyboard. Would I do it? No. First, you would have to bring around the iPad and an external keyboard with you. Typing isn't horrible with the virtual keyboard but there's no 'tab' key which I use a lot while taking notes in class. Also, sometimes apps crash, and I don't think there's an automatic save feature on Pages for iPad (like on Word) that periodically saves your work in case it suddenly crashes. I love my iPad, but another reason I would never use it to take notes in class is that I think I would look ridiculous. Right now, I think the iPad is just a laptop/computer supplement rather than a replacement so if you're between a Macbook and an iPad I'd go for the Macbook.
I disagree. I think if you get an apple case, or one similar, that lets you prop up the ipad to a slight angle, typing would not be much a problem at all. You could simply place the ipad on your desk then and comfortably type, not needing an extra physical keyboard.
I don't know about the save feature, although I'm sure 3rd party apps would most likely include something like that, even if pages didn't. I think the basic notes app on the ipad saves automatically, since there is no save button to press.
As for it looking ridiculous, I don't know, I think with the case that props it up on an angle, it would look quite sleek and I think as more and more people use their ipads, it will just become part of life to see people using them for pretty much everything.