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.
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