Of course, these only work for packages the distribution includes - you might still have to download sourcecode and compile and install manually.
Since gentoo is a source based distro (when you emerge a package, portage downloads and compiles the source for you), it is very easy to create your own ebuild (the gentoo package tyoe) if there is a package you want that's not in one of the repositories, or you want a newer bleeding edge version than currently in the repository,
It's also easy to create your own .deb packages and RPMs. The fact that gentoo is source based doesn't give it a monopoly on creating packages easily. My point was more about something that most of new users of linux come up against at some point - they want to install a particular program, but there is no package for their distribution for it. In many cases, there are already packages available anyway, or packages for a very similar program. Hopefully this will get covered at the next meeting.