This http://stackoverflow.com/questions/1033897/python-package-install-using-pip-or-easyinstall-from-repos points out a very interesting features of pip.
However, sometimes you just want it to install the source distribution; this is particularly true when
- you are running in a virtualenv (so you don't care about messing up the python path, since you are deliberating doing it in an env),
- when you are not the developer of that particular package, and you don't want to have it "editable",
- when you cannot pip install package-name because the package is not in any index,
- when there is no tar.gz available.
Thanks for your answers!