Similarly, you should avoid updates from Unstable when Debian is in the middle of a transition from one technology to another. For instance, some years ago, Debian switched from XFree86 to X.Org for graphical display, and it took a while to make the transition seamless for users.
If you use Unstable as your chief repository or occasionally borrow from it for a hybrid system, you need to get into the habit of watching what the project is doing.
For instance, when a release freeze has just occurred is generally a poor time to update or install unstable packages because some might have been made in a hurry in order to make the freeze deadline.
Under these circumstances, for a week or two you might want to use the -s option for apt-get to simulate an update before actual making it, just to avoid trouble.
The truth of this assertion depends on the repository and the circumstances.
Generally, the Stable repository is much more likely to be out of date than Testing, which is more likely to be more out of date than Unstable. Historically, two or three years have sometimes passed between official Debian releases, and just before a new release, Stable can be very obsolete, although micro-releases, backports and security patches continue to make it usable.
Similarly, when a freeze is on, leading up to a new release, the contents of Testing and Unstable become increasingly identical because no new packages are entering the system.
Conversely, in the first six months after a release, Stable can be as current as the repository of any distro.
What is true is that the availability of packages depends on the enthusiasm of the maintainer teams. Popular applications like Amarok can be in Unstable days after the upstream project announces a release.
Other packages may take longer to appear. Debian's emphasis is the stability, not the currency of its packages. If you really want the latest software, you can enable the Experimental repository, but not every package that goes into Unstable goes into Experimental first, and the repository can cause serious problems.
In general, though, the currency of Debian's packages is a minor concern at best. While everyone likes the idea of having the latest version of everything, most apps on the free desktop are advanced enough that the differences between one release and the next are minimal most of the time.
You won't find Debian in the Free Software Foundation's list of free-licensed distributions for two reasons: first, because each Debian repository contains a non-free section, as well a contrib section consisting of software that is free in itself, but depends upon non-free software, and, second, because it includes the option to install proprietary firmware in its kernels.
However, the Debian installer encourages users to install a free system. Those who want to use the non-free and contrib sections have to add them to the list of repository sources themselves. Similarly, users can choose not to use proprietary firmware when they install. With these options, you can easily install a free Debian system if you choose.
A complete version of Debian fills fifty-one CDs and is likely to take twenty-four hours or more to download.
However, most users download a live CD, a network install image of 180 megabytes, or a business card install of 40 megabytes. It takes longer to complete an install with these solutions because they have to download from the Internet what they do not have. But with them, you can be ready to install in five minutes or less.