Something that I always thought was a bit wrong with OS X was that there seemed to be no way of un-installing a .pkg file once you installed it. As a result I tended to avoid software that used .pkgs and instead opt for software that used the more standard OS X technique of being entirely encapsulated in a .app file with no installer. Not anymore thanks to OSXGNU.org!

OSXGNU.org have created a nice COCA GUI to allow you to easily install and more importantly un-install .pkg files. It is an absolute must have and comes it self as a .pkg and installs it self in the Applications folder under Utilities.

You can download it here: http://old.osxgnu.org/software/Utils/OSXGNU/

Here is a screenshot from their webpage: