Yeoman is fantastic...I used it several months ago when deciding (foolishly, in retrospect) to learn both CoffeeScript and AngularJS at the same time while making an app. I had never put the effort into setting up grunt tasks manually...so working with automated building and testing were things I never had while developing with JS (which you can take to mean that my past work with JS has been mostly trivial).

Besides just being a great package overall, Yeoman really helped me appreciate how what seem like trivial niceties -- the speed of auto-build vs. stopping and restarting the local server and hitting Refresh -- can really make the difference between gradually losing interest because of the accumulation of small inconveniences and actually enjoying the development process enough to finish a project.