It took a bit of arm-twisting for me to realize why anyone would want a packaging system on OS X. After all, it goes against the idea that we can just move app bundles wherever we want. Or, we could just compile from source, like people did for years on SunOS and IRIX (before Linux and the explosion of package management systems).
OS X has a unique BSD heritage, and there are more quirks than you can shake a stick at. It's a small price to pay for the legendary Apple GUI, but working around those quirks for each new program can be tedious.
If you only install one or two Unix-style (versus Mac-style) programs from source, you probably won't find Fink to be worth the trouble. On the other hand, if doing something more than a couple of times in a shell makes you think, "I could write a Perl script to do that...", then you might benefit from the automation that Fink provides.
Why compile from source?
Fink provides a great environment for making sure that your compile goes smoothly (assuming the packager did their job correctly). But in the end, you have a bunch of binary packages that you could have just downloaded from somewhere. Why would you bother with compiling from source, given the added time and chance for error?
Part of the beauty of open source software is that you don't have to wait for an officially sanctioned release to get bug fixes. You can get your hands dirty, and fix it yourself, if you are so inclined. (Often, patches will surface on a mailing list.) And the binary packages are almost never as current as the source code.
What on earth inspired you to do this?
I'm not totally sure. Back in grad school, when time was more abundant than money (but after I had already purchased a Mac), I worked on various electronics design projects. Since my Mac was several times faster than my laptop, I wanted to have access to the same EDA tools that I had in Linux, but without installing Linux on the Mac. (I'm a sucker for Aqua.)
Common sense would have dictated that I stop after I got them to compile once, but eventually I put together some Fink packages.