The Debian Project's key strengths are its volunteer base, its dedication to the Debian Social Contract, and its commitment to provide the best operating system possible.

Debian GNU/Linux 4.0r4 adds security updates, miscellaneous bugfixes, missing builds, an updated release of the installer, and a few corrections to serious problems.

Debian GNU/Linux 4.0 comes with a lot more software than its predecessor (Debian "sarge"); the distribution includes over 6500 new packages, for a total of 18733 packages precompiled for easy installation.

Debian GNU/Linux 4.0 includes over 10700 updated software packages, such as KDE 3.5.5a, GNOME 2.14, Xfce 4.4, GNUstep desktop 5.2, X.Org 7.1, OpenOffice.org 2.0.4a, KOffice 1.6, The GIMP 2.2.13, Iceweasel (an unbranded version of Mozilla Firefox 2.0.0.3), Icedove (an unbranded version of Mozilla Thunderbird 1.5), Iceape (an unbranded version of Mozilla Seamonkey 1.0.8), PostgreSQL 8.1.8, MySQL 5.0.32, OpenSSH 4.3, GCC 4.1.1, glibc 2.3.6, Linux kernel 2.6.18, Apache 2.2.3, Samba 3.0.24, Python 2.4.4 and 2.5, PERL 5.8.8, PHP 4.4.4 and 5.2.0, Asterisk 1.2.13, OpenLDAP 2.3, and thousands of other ready to use applications.

Debian GNU/Linux 4.0 also features cryptographic software and compatibility with the FHS v2.3 and software developed for version 3.1 of the LSB.

Debian GNU/Linux 4.0 switched from XFree86 to the 7.1 release of X.Org, which includes support for a greater range of hardware and better autodetection. This allows the use of Compiz, which is one of the first compositing window managers for the X Window System, taking full advantage of hardware OpenGL acceleration for supported devices.

Using a fully integrated installation process, Debian GNU/Linux 4.0 comes with out-of-the-box support for encrypted partitions. A newly developed graphical frontend to the installation system supports scripts using composed characters and complex languages; the installation system for Debian GNU/Linux has now been translated to 58 languages.

The package management system is improved regarding security and efficiency. Secure APT allows the verification of the integrity of packages downloaded from a mirror. Updated package indices won't be downloaded in their entirety, but instead patched with smaller files containing only differences from earlier versions.