I may be a bit biased because I really love this app, but it helped me a lot to stop throwing money on useless things.
Side note: Jesse (founder of YNAB) is an amazing speaker with a great sense of humor. His story about bootstrapping YNAB is hugely inspiring to me. I highly recommend his 2014 Microconf talk (https://vimeo.com/95653848) if anyone is interested.