I'd say it's an essential - some lecturers at my uni don't give printouts and expect students to bring laptops so they can access slides in class, complete online quizzes during, and other things. Between class you have the libraries to go to and again the PC space is so limited that you'll regret not having a laptop with you. Teamwork can also be popular at uni, and a laptop in team meetings is again important.
Plus, you'll be able to work on the train.
Not to say it's impossible, but it's often assumed you have one.