The fun thing about lightweight, painless branching is that once you start to incorporate that into your workflow, it's never too early in a project to use it. Lately every new feature or fix I start to work on begins its life in a topic branch. You never know when you're going to be interrupted or need to switch contexts to work on something else (or even just scrap the whole idea) so having your repository mirror your mental process in a completely seamless way is invaluable.