In my most humble opinion, one its biggest advantages is this:
What happens when the application you are looking for is not in your distribution’s repositories? If you run Fedora, you might need to add an unsupported 3rd party repository of questionable quality. If you’re running Ubuntu, you hope for a Personal Package Archive. Sometimes you just have to compile from source, and endure the heartache of dependency resolution. On Arch it’s pretty simple. Chances are that the app you are looking for is available using a PKGBUILD script from the Arch User Repository or AUR. A PKGBUILD is a script created by a member of the Arch community that takes much of the pain out of building an application from source. The makepkg command runs the PKGBUILD script, detects and installs dependencies, and builds a pacman installable binary package. There’s no need to search for any obscure libraries that may not be installed in the core package list.
The only thing that should have been mentioned is the Arch Build System. But a good reading nonetheless.