I've never seen the upside. I use Emacs as my primary editor, and I regret it every time I say "today is the day I start using Magit". It is exceedingly invasive, triggering itself even when you don't ask for it (like running "git rebase -i" on the command line). The invasive stuff changes how the text editing itself works, but doesn't add deep features. In the interactive rebase case, I lose the ability to treat the interactive rebase text as text, but I also don't gain anything. I can't just navigate around, kill a line, and put it somewhere else. Well, I can do that, but the usual keybindings don't work, they just made their own for no reason. And, for example, if I do use their UI and pick "reword" as the operation for a certain commit, I should be prompted for the desired rewording then and there, right? But that's not what happens, I press C-c C-c to commit my changes (why isn't it C-x # which is how I'd normally close an emacsclient session?), then Emacs goes away, then it comes back up, then I can type my rewording. If you pick it more than a few times, you just get a seizure from all the flashing lights. This isn't a good user interface. It's a bad user interface.
Obviously, my experience must be unique, because everyone loves Magit. It might be the most-loved piece of software ever. Every other week, there is an article on Hacker News about how it's the best piece of software ever to exist, and I've never seen anyone say anything bad about it. So I wonder what marketing techniques they use to make people feel this way; the emotions are strong, and widely shared.
Maybe there is some fundamental insecurity about Git, and Magit makes people comfortable? I've never felt that way, but I did start using Git the weekend it came out, and my Github user ID is in the low 2000s, so I might have had time to get Stockholm Syndrome with the Git UI. I suppose it's possible that the people writing these articles may not have even been born when Git came out, which is interesting to think about actually!