The first two things I immediately noticed is that SkySafari Pro 6 scrolls haltingly through observation lists, and that the screen controls (in particular, object selection and direction buttons) freeze while controlling the telescope.
For telescope control, I use the Celestron Wifi connection. I first suspected Wifi signal problems and/or iPhone performance problems due to cold temperatures. However after further experimentation and experience, I am more inclined to believe that both problems are due to underlying background task issues. I concede that it is still possible that there may be Celestron Wifi issues involved. But by and large working with observation lists is associated with freeze up problems Wifi or not. At this point I probably have about 4000 observations, most migrated from SkySafari Pro 5. On the other hand, I have been using a hand warmer with the iPhone, and I find that I normally don't have freeze up issues while controlling the telescope unless I work from observation lists.