I'm a big OneNote fan.
I only got it right before the start of my 1L (this) year. I acquainted myself with it over the week or so prior to classes.
One of the biggest advantages (in my view) is that I can flip between case briefs, notes, outlines, etc... from every class all within one big frame...I don't have to open additional files, navigate folders and wait for word to load up the next file, etc...
That alone makes it worth it for me.
Additionally, I can easily search an entire folder of files. For instance, I have all my case briefs in one tab. When my CrimPro prof says "what other case have we discussed that seemed similar - when they discussed the use of a K-9 unit during a traffic stop?" and with one 3-second search, I can have all the tabs highlighted that contain "K-9" or whatever search term I include.
Additionally, I can easily print one page, one tab, an entire folder, etc... with just a couple of clicks.
While the CTRL-F find in word is pretty easy, believe it or not, it is even easier and friendlier in OneNote in my view.