If you use the amazing unite.vim plugin and noticed it being anything less than snappy, then you need to make sure you have vim with lua support enabled.
You can see if you copy of vim has it enabled by running
:version and looking for
+lua. If you see
-lua it is not enabled. The main download binary for MacVim does not have it enabled.
The solution for this is simple, install MacVim from Homebrew with the
--with-lua flag. The exact command I use is:
brew install macvim --with-cscope --with-lua --override-system-vim
That will install with lua and cscope, and will put a symlink in
/usr/local/bin that will shadow your system command line vim. All good things. To see the other options check out the homebrew formula.