In most of the code bases when 5+ people work on the same code, it's really hard to add some non-trivial functionality by writing it the proper way from the beg

In most of the code bases when 5+ people work on the same code, it's really hard to add some non-trivial functionality by writing it the proper way from the beginning. BTW I think sticking with the attitude "first specs, then code" is old school in most situations. Some very rough spec will be fine, but a lot of the things you haven't thought of, you encounter while actually playing with the app/widget, or stepping through the debugger (unless you've worked on a product for a very long time and know it inside out). I find "write working code & then refactor" ridiculously easy when working with Git. Add some tiny new things one-by-one and commit early each time it is more or less stable (so you can revert quickly when you screw it later, instead of doing some crazy debugging). When it's done, squash the commits and refactor.