The mini with Retina display easily gets the 10 hours of battery life Apple advertises, and that’s with heavy, constant use; in most cases the battery should easily last three or four days. There is one notable exception: with brightness all the way up.
I’m getting used to the core tenets of iOS 7. I still don’t like the slow animations or the often-needless representations of layers and transparency, but I’ve come to understand the OS for what it is. As we discovered with the iPad Air, though, iOS 7 isn’t finished or polished.