Alan is hesitant to upgrade to iOS 8.4 because he's heard that Bluetooth doesn't work when connecting his lighting cable in the car. Leo says that it's a noted issue on the support boards. But Leo says it will likely be fixed with the next update and iOS 9 is coming this fall, so it won't be long if there's a bug out now.
He could try the public beta of iOS 9 which is out, but it is a bit buggy. In fact, Leo recommends just not upgrading. The only thing that iOS 8.4 really did was update Apple Music. That, and the Twitter bug is also fixed.