As usual upon a major Emacs release, Mickey Petersen, of Mastering Emacs fame, has an exhaustive listing of what’s new in the release. His post is an annotated version of the NEWS file so it is very long and detailed. It’s much too long to cover in detail here so you should take a look at the post itself.
The big news, of course, is that native compilation is now an official feature of Emacs. That change should speed up almost everything you do in Emacs because it compiles Elisp into native code. You need to specify --with-native-compilation when you run configure prior to compiling Emacs.
Besides native compilation, there are many many smaller changes. One—that isn’t mentioned in the NEWS file—is that they fixed the interaction with macOS Monterey that made Magit interaction run slowly on Macs. It’s a huge relief to me to have that fixed.
Among other interesting changes are the inclusion of the Ctrl+x x keymap that includes functions for buffer actions such as revert-buffer-quick, rename-buffer, clone-buffer, and others. Sadly, it appears that the Bookmark+ package grabs the Ctrl+x x prefix so that’s something that I need to resolve.
I also like the new binding Meta+s Meta+. that starts an isearch for the thing at point.
As I said, there are a huge number of new and changed features. Any given user will find many of them interesting and many of them of no interest at all. A quick reading of Mickey’s post is a good way to discover which changes are interesting to you so that you can investigate them in more detail.