At one point source depot was Toincredibly advanced, and there are still features that it had that git doesn't. Directory mapping being a stand out feature! Being able to only pull down certain directories from a depot and also remap where they are locally, and even have the same file be in multiple places. Makes sharing dependencies across multiple projects really easy, and a lot of complicated tooling around "monorepos" wouldn't need to exist if git supported directory mapping.

(You can get 80% of the way there with symlinks but in my experience they eventually break in git when too many different platforms making commits)

Also at one point I maintained an obscenely advanced test tool at MS, it pounded through millions of test cases across a slew of CPU architectures, intermingling emulators and physical machines that were connected to dev boxes hosting test code over a network controlled USB switch. (See: https://meanderingthoughts.hashnode.dev/how-microsoft-tested... for more details!)

Microsoft had some of the first code coverage tools for C/C++, spun out of a project from Microsoft Research.

Their debuggers are still some of the best in the world. NodeJS debugging in 2025 is dog shit compared to C# debugging in 2005.