One of the more subtle changes often made, other than adding non-Debian repositories, has very important implications. Note that the release name in most of the lines from the previous Debian release sources . list is wheezy. This means that the packages available through the package managers will always be from the Debian 7 release. Some administrators change the release name to stable. This has both advantages and disadvantages.
One advantage is that, when a new major version is released, your package managers will immediately recognize this and update package lists and dependencies accordingly. The disadvantage related is that major releases involve major changes in package dependencies. While package managers can handle this, such major changes usually result in many new packages being installed to satisfy new dependencies, many old ones being deleted due to changing dependencies or obsolescence, and major version changes that often change the way the software behaves. These changes can be quite disruptive to server operation, or to developers' or users' habits.
Best practice to ensure stability is to leave the official release name in place until you are ready to upgrade to the next release. Then change the name in the package manager configuration, and perform a manual upgrade.
