Off the top of my head: Tree view in PRs, the new projects board, code search, Mermaid and maths in markdown, the cmd+k action bar thing, Copilot, the best VS Code themes, lots of small changes like Readme TOC, and so on.

Maybe these changes are incremental, maybe you don’t cherish them as much as I do ,and some were very much over due. Regardless, I like them and am impressed by Github’s recent work.