Yes, there are plenty of people using Vim or Emacs as they're primary editor. You don't always hear from them though, because they've already lived through several rounds of editor wars.
I'm really embarrassed that "their" ended up "they're". I'm not sure if I typed it out of muscle memory, or if I mistyped it and Lion auto-corrected to "they're".
This is why I never stoop to pedantry. I know the difference, I swear!
I made my editor choice over 20 years ago, before these things were even a glimmer in their creators eyes. The key sequences I use for editing are cast in stone into my muscle memory, and serve me in nearly every command-line tool I use, as well as every text entry widget in OSX. My editor is part of my hacker DNA.
I use Emacs on OSX, just like I do on every other operating system I have to use.
I'm more than happy using a combination of Vim (not MacVim) and tmux on OS X. I was spending more and more time in the terminal (running tests, committing changes, etc.) so it made sense to me to incorporate Vim into the window as well.
FYI my transition was Notepad++ > TextMate > Sublime Text 2 > Sublime Text 2 + vintage mode [1] > Vim.