I would recommend you get something. You never know when you need to have 3-5 books on you at one time. LIke finals.
I agree with this assessment.
I normally just had my laptop/sylabi/other misc. in one laptop bag, and carried my casebook in my other arm. That worked well for 85% of the time, but it was a pain when I had a morning class that went to 11:50, an afternoon class that started at 1:10, and a lunchtime event that I wished to attend at 12:00. On such days, I found the ten minutes allotted to locker trips just weren't enough. I recommend getting a backpack or rollybag large enough to hold 3 casebooks for such days.
Also, everyone should get a locker in the 198 building, even if you live in the Tower. I rarely used mine, but was very thankful to have it on the days that I needed it.