To be specific, magit enables a couple of incredibly useful workflows, like the "what changes have I made that are outstanding? review them, jump to the file in question to gain additional context if confused, stage individual changes and THEN commit" workflow (a compelling way to review your work for bits you'd forget with commit -a and far more convenient than git add -p), the "darnit, I just lost my place in the code again -- I know, I'll find it in the diff and jump to the line" workflow, and a number of other interactive repository history-viewing workflows.

The functionality provided by magit and a couple clever hotkeys to find code and run tests have proven in my own experience to be excellent foundations for developer productivity in any medium-to-large sized codebase.