I've a UITableViewCell designed with .xib that use cell autosizing. In iOS 9 works well, but in iOS 8 cell doesn't expands itself, and the label inside remains with 1 line of text. If the cell go away from the screen and the came back (i.e. after a scrolling) all label are ok.
edit:well, I guess the joke is on me for assuming the question was about swift instead of obj-c(didn't notice the tag).
Because I think my answer is still useful(for other people that is)...I'm going to leave it here.