tl;dr: Julia 1.13 delivers ~30% faster package precompilation and ~20% faster startup than 1.12, plus dramatically faster full GC by skipping never-freed sysimage/package-image objects during marking (e.g., 35ms → 2ms in a bare session). The REPL gains built-in syntax highlighting and fzf-style history search, hashing switches to Rapidhash for major speedups, and scheduler fixes restore reliable Ctrl-C interrupts. Pkg gets a faster resolver, zstd downloads by default, and prefers already-loaded package versions to avoid needless recompilation; Juliaup also ships a new GUI.