Let's look more closely at the kind of competitive edge the Tablet PC can offer a student.

Things you can only do with a Tablet PC
Okay, we're talking about Ink; the ability to write on the screen.

This gives you the ability to make notes in the same way you can on paper. The picture at the top of this article is a quick sketch someone might have made during a lecture on black holes. Can you imagine trying to capture this as text, by typing?

Annotations
Course materials that are available in electronic format do not have to be printed before you can make notes (annotations) on them.

Ink annotations can be searchable. Imagine plowing through printed materials looking for handwritten notes where you wrote "exam" beside a key point. Then imagine being able to search for them. Even things you had written in ink.

Non-Text Notes
That strange diagram at the top of this page captures the idea, but here are some other things that you can do in Ink naturally that can be a challenge in text.

Diagrams, charts, mathematical forumulas, tables of data, Mind Maps. Yes, you can do all of these on a keyboard if you have lots of time, but doing it live, in real time while a professor is talking. That's another matter.

Work Anywhere
With a Tablet PC, you don't have to find a good place to work. You can basically work anywhere: at a desk or table, on a couch, on the floor, while standing, even while walking (although you might have to dump your chewing gum first).

Tablet PCs are environmentally friendly?
I have often witnessed and experienced the hostility directed at people who are banging away on a keyboard. Inking is no noiser than writing on paper.

Any Tablet PC in slate mode (with keyboard removed or folded away), is going to take less space than a similar notebook computer while in use.

Back to the point
If your student takes advantage of even one of these features of a Tablet PC, she or he has an edge over the other students. 

Isn't that worth the price of a cup of coffee a day?