I use this frequently as part of my teaching. It was necessary to be able to properly deliver information to students online.
This is one of the absolute best products in its space. I have tried to find free alternatives, but nothing compares to the features and functionality of EE. It is definitely worth the money if you are an educator teaching online.
I wish that some of the drawing tools were a little bit more powerful, but aside from that, no real complaints. Given that it is more for annotating / writing notes, I can see why the pure drawing features may not be at the top of the list of priorities.