What is the easiest way to install emacs-ess on OSX? I am interested in installing Emacs ESS mode. I can follow the instructions here but I would like to know if there is an easier way (without installing a completely new instance of Emacs like the one provided here). 

For example, the instructions say that I can use the Linux version, but then I don't know if I should use the Debian, OpenSUSE, or Fedora package listed on the Downloads page.

This is a specific example of a situation alluded to in my previous question that was closed because it was too general to be constructive.
Use the latest .tgz package:

Here is the installation version from the documentation (the -12.09-2 part of the file name is current-release specific and will change):

wget http://ess.r-project.org/downloads/ess/ess-12.09-2.tgz
tar -xvf ess-12.09-2.tgz
mv ess-12.09-2 /Applications/Emacs.app/Contents/Resources/site-lisp/
echo "(require 'ess-site)" &gt;&gt; ~/.emacs