I just recently started using Angular, but ui-router definitely gave me a bit of trouble. I had to dig through StackOverflow to find answers to questions like how to enforce that certain views must only be accessed when the user is logged in. Another bit of trouble I had was doing things like logging the user out, then immediately redirecting them to the login page. Had to redirect then to the home page so that the state change hijacking code fired and redirected a second time.

I can definitely see that ui-router is a valuable component and it's very powerful, but perhaps I have not achieved the zen of it yet.