If you are a student, an iPad is the best gadget you can bring to class. Purchase one if you can afford it. It is worth every cent and more.
The issue goes beyond form factor and portability. I will deal with the hardware issues later. It is the apps that are dead useful.
Apps
Evernote
Firstly, Evernote. It is life-changing technology. The app practically runs my life. For the purpose of school, I download all my course and research materials to it, and I save the notes I take in class on it. I can take photos to accompany my notes, or sketch freehand. I can also do an audio recording during my note taking. One copy is in the cloud and I can download as many copies to as many devices as I want. This means I can work on my assignments or catch up on reading whenever I have my iPad with me. Everything is auto-synchronised. With Evernote, which is both Windows and Mac compatible, I never lose my stuff. Another beautiful feature about Evernote is its search engine. Install the Web Clipper on your browser. While you do your Google search, Evernote does a simultaneous search through your materials which helps you recall what you have studied. You can clip entire webpages to Evernote for ease of retrieval. You can also forward or cc/bcc emails to Evernote for the same purpose. (Update: The simultaneous search feature is not as reliable as of 15 April 2017 but the search function within Evernote itself is still good.)
Notability
For occasions where word for word accuracy is required, I prefer taking my notes on Notability and send it to Evernote later. Like Evernote, Notability is able to do a simultaneous recording as you type. It goes one up on Evernote because after you have completed your notes, you can go back to the exact timing of the recording when you were typing that word. You do not have to scroll through the entire sound clip to search for what you need.
GoodReader
Most of your reading materials will be in PDF. Even though Evernote has PDF annotation features, it messes up the sort order of my notes, which I hate. I prefer to use GoodReader to handle my PDF files. You can highlight text, type annotations, underline, write or draw freehand using the app.
Other apps
Other apps you will find useful for school which need no further description are Dropbox and the Microsoft Office apps.
Hardware
Do you need to buy a keyboard for your iPad? No. It defeats the convenience of toting a slimmer and lighter alternative to a laptop. It is not difficult to type fast on a tablet, especially with predictive text.
You will find a stylus useful for sketching, highlighting dense text in PDF files and other freehand work.