One of the benefits of Debian is that it is very easy to upgrade, both between distributions (i.e. upgrading to a completely new version of Debian) and within distributions (i.e. updating to the most recent version of a program). All it takes is two little commands ("apt-get update" followed by "apt-get upgrade"), and Debian automatically auto-detects what packages (programs) have newer versions available, and whether installing any of those newer packages would break or conflict with any of the packages already on your computer. Debian then shows you a list of the programs it will upgrade, and assuming you approve, Debian downloads, configures, and installs all the new packages.
The big advantage of Debian's package management system over anything I've seen for Windows is that this routine upgrades every single program on the computer (assuming the program was installed via a Debian package, of which there are thousands). You don't have to go to a separate website to update the operating system, the virus scanner, the office suite, etc; it's all done via the same single command.
I'm currently running the testing distribution of Debian (see here for a discussion of the distributions), which means that while I am able to use relatively new development versions of most programs, some of them might be a bit buggy. I haven't run into many problems while updating, but after I upgraded all the packages on my system last week I discovered that the latest version of Firefox in Debian's testing distribution crashed when I did just about anything.
But there was nothing to worry about, as the Debian package management system came to the rescue. All it took was one command ("apt-get install mozilla-firefox=[insert-prior-version-number]") and I was back to my nice, stable version of Firefox. There was no complicated uninstall and reinstall, no worrying about my configuration files (all plugins, bookmarks, and other configured items were left unchanged), and very little stress. I even found that bug reports had already been filed (at bugs.debian.org), so hopefully the problem will be fixed in the next testing release.
In fact, if I'd been really smart, I would have checked the bugs list first, seen that there were grave bugs filed for this latest version of Firefox, and decided not to upgrade. But I'm not that smart.