The only usability issues I've had with emacs on mac, and it's a mac fs thing, is that at a certain point I would get a "too many buffers open" (assuming handles to files open) issue and it wouldn't run any commands whatsoever, I'd have to somehow clear the buffer list to get it to work. I think there was a setting I ran in the console to increase that limit for the filesystem, it was months ago so I forgot what solution I used.