Admittedly, I have not taken the time to try MacPorts specifically. (This is probably due to the fact that the lab machine I worked on was polluted by various things installed via MacPorts, which seemed to mess with the autotools/configure process even further, if I was trying to compile something in ~/src. Left a bad taste in my mouth. But that's obviously not MacPorts' fault.)

My experience is that these third-party package managers are great, until you want to make them work with software that doesn't come through the package system. A good test case, I think, would be this: how easy is it to install Python via [MacPorts|Fink|Homebrew|etc.] and then compile and run the latest SciPy (say, a bleeding-edge version from source control, not one from the package manager) against that Python?

Can you speak to a case like this, or one of similar complexity?

Hmm. I've never used SciPy before but let's see if I can figure it out:

$ brew install python pip gfortran # Fortran's for scipy...

$ pip install numpy

$ pip install svn+http://svn.scipy.org/svn/scipy/trunk/#egg=scipy

If you don't want to use the SVN version of SciPy, you can just use:

$ pip install scipy

Homebrew and pip are the first things I've ever used that made me not miss apt on debian.

Generally, it just means that you need to get your prefix set up right.

I've used MacPorts to install one dependency for something I was compiling by hand, and so I sort of did the opposite: I told MacPorts to install that particular package into the directory where I had hand-built the rest of them.