"90% of iOS apps tested for first time are having trouble," said Matt Johnston of the app-testing firm, uTest. What they're finding is that iOS 7 crashes apps that haven't upgraded properly, and developers are having to make three or four attempts before they've gotten it right.
This is particularly true of apps for iOS 6 that use the swipe-up feature. Eventually all of these will likely get up to speed, but it just won't be from Day One.