As usual—with every Linux distribution, really—the biggest changes you’ll notice are package updates.
The majority of the packages included with Debian have had their versions bumped to the latest ones. From desktop environments and desktop applications to server software, system tools, and libraries, Debian now includes more of the latest software. Debian 7.0 Wheezy was released back in 2013, so there are about two years of new software included along with Debian here. New versions of Debian and Linux distributions don’t just bump package versions—all these bits of software from different projects are tested to make sure they work properly together and form a stable system.
The old and insecure SSLv3 protocol has been disabled across this release, with system cryptography libraries and applications compiled without support for it. Many packages are now compiled with more “hardened” compiler flags for security purposes—these provide additional protection against buffer overflows and other attacks.
But it’s not all bad news if you loathe GNOME Shell. Along with the usual universe of Linux desktop environments, the MATE and Cinnamon desktops popularized by Linux Mint are also available in Debian Jessie.
This is the release that sees Debian switch to systemd from the old SysV init system. It was previously included with Debian 7 Wheezy as a technology preview, but it’s now the default for everyone in Debian 8. The Debian project had to switch to something, and systemd won out. Ideally, you shouldn’t notice any differences. Even if you’ve written your own SysV init scripts, systemd is designed to be a drop-in replacement that supports all your old scripts.
This decision was made after much drama and debate, and the Devuan project is upset about it and working on forking Debiansans systemd. But it remains to be seen if Devuan has enough staying power to bring together a large number of people to spend years on creating a forked version of Debian. It’s a huge job.
Debian is just the latest Linux distribution to switch to systemd. Ubuntu just switched to systemd with Ubuntu 15.04, for example. Fedora, Red Hat Enterprise Linux, openSUSE, Arch, and various other distributions have also adopted it in the past.
Debian should just work on more PCs
Modern computers that use EFI boot mode instead of BIOS boot mode have been a bit of a pain point, but Debian 8.0 Jessie has seen a lot of improvements here. Computers with broken EFI implementations should now be handled much more gracefully. Debian Jessie should even boot and install on Intel-based Macs without any additional third-party software. This hopefully isn’t something you’ll even need to think about. Debian should “just work” on more computers, just as the latest version of the Linux kernel should make more hardware “just work.”
Across the nearly two years of updated packages with various improvements and bug fixes, there are many more changes—far too many to list. Check Debian Jessie’s official release notes for more detailed information.