They really should have added CPAN (for perl) to their list. Perl might not be the most popular language nowadays, but in my opinion, their package manager gets a lot of things right...
* centrally hosted
* mirrored all over the world
* packages are automatically checksummed & the checksum is compared on install
* is is quite easy to publish packages
and very important in my opinion
* it encourages you to write tests. Unit tests included in packages are automatically executed when it is installed. Many systems (semi)-automatically report back when the installation of a package fails. Hence you get tests on tons of platforms for your package
* pod documentation is automatically available on cpan.