For me, being able to go straight from a selection in a code file to a log of all changes to that specific code, which I can then filter further, is what gets the strongest reactions from my coworkers.
WHAT!? You can use M-x magit-log-buffer-file with an active selection and see only the changes to the selected portion? This is so obvious in hindsight and so cool... Thanks a million!
It's unfortunately hidden because it has no default keybinding iirc, but I love this feature. I think I discovered it by wondering if it exists, so I searched through the M-x candidates with orderless and typed in terms that I guessed could be part of the right name.
The documentation is very good. The Getting Started[0] page has all you need for basic operations. I haven't watched this particular video[1], but Prot's other Emacs content is great.
I watched the video. It is quite informative. The best thing about emacs videos are they creator is that all the keycommands show on the screen by default. Arguably one of the slickest features in emacs.