It was heaven. I could write at my normal speed. If I made a mistake, one tap of a button erased it, faster than if I were using a pencil. Then I could select symbols by just drawing through them, then copypaste them a line below without worrying about copying errors like dropping a sign. If my writing started to get too messy or cramped, I could just drag things around. And I could change colors of things anytime I needed, which helped me reason through a lot of things.

At least when it comes to math and manipulating symbols (e.g. proofreading marks), it's not the screen that's the problem, it's just the keyboard and mouse.