Magit hasnt been slow for me since I upgraded to Emacs 26. Older versions of Emacs were not optimized for spawning processes on OSX and it was causing a 10x slowdown for some operations.
Perhaps I should revise my statement. It isn't magit itself that's slow, but rather magit is calling out to slow git commands. And while those git commands are taking up 100% of my CPU, Emacs itself is using 0% CPU and totally unresponsive.
Just a few moments ago I had to kill Emacs because magit was executing this command:
That particular issue has been fixed a few weeks ago. You should update Magit. Also you should be able to avoid killing Emacs by just pressing C-g a few times if some subprocess takes a long time.
Magit hasnt been slow for me since I upgraded to Emacs 26. Older versions of Emacs were not optimized for spawning processes on OSX and it was causing a 10x slowdown for some operations.