Great for file sharing
My take is pretty much the same as how I use it. It is another way to do what Google Classroom can do, but works better for me because I have iPads and Notability. Without Notability, it would not be nearly as useful.
How I Use It
I use this to share documents and other files with students and have them submit their work to me. I know many teachers are using Google Classroom - and I do as well, but using Dropbox paired with Notability works much better for me. The students can get a document from Dropbox, write on it with Notability, and turn it in to my Dropbox. My files stay organized and the kids have mastered this process.