One major problem that I foresee with the X is the battery life. Of course, no one knows how it will fare in the real world, but one of the main reasons why I upgraded from the 6 to the 6s Plus was the atrocious battery life of the former. Based on the specs released by Apple, it seems that the X's battery life will be a lot closer to its smaller counterpart, rather than the larger one. I don't like battery cases, so the potential of poor battery life is a real issue.