tl;dr: Emacs 31.1 ships as a collection of quality-of-life improvements rather than a headline feature, with the planned new garbage collector pushed to Emacs 32. Notable changes include the final removal of the deprecated unexec dumper, a new `user-lisp/` directory that auto-loads and byte-compiles packages, tree-sitter grammar auto-installation, terminal child-frame support, xterm mouse mode on by default, window layout rotation commands, and numerous minibuffer/completion refinements building on Emacs 30's native completion preview.