It's a UI layer on top of an old-fashioned bank. It offers worse rates, perks, benefits and service than Ally, Schwab or Fidelity. Good if you want something pretty on the side, I suppose.
I havent used the app but Simple sounds pretty good since you can set multiple "goals" (I think they should call them buckets or envelopes or something).
Also, they offer a JSON feed of my transactions, which isn't something any of my other banks provide.
It would be nice if they had OAuth support or a formally documented API, but it's still a good start.