Known thing my app starts slower on iPhone 4 with iOS7 then it is on the same iPhone 4 with iOS6. This is pretty sad, but not the only sad thing...
As I'm profiling now the app before its soon to come release to AppStore, I got to the following screenshots for the fresh app start on iPhone 4 with iOS6:
Note the 1.55MB number. And now, the sad thing, same fresh start on iPhone5 with iOS7:
Noticed that 8.21MB?! I currently only have iOS7 installed on iPhone 5, so I can't compare iPhone 4 iOS7 vs iOS6 consumption, but I believe this iPhone 5/4 factor should not play any role here. It is just iOS thingy.
While not that sad for iPhone 5/5s, it is pretty bad news for my users that are still on iPhone 4, apps are going to consume more. All apps, not only mine... App startup is becoming definitely heavier and those extra allocations in iOS7 are surely standing for more work done by iOS7 while starting the app.
Having read Steve's biography, it looks to me like a step away from the "saving lives" approach to plain MS's "throw more memory on it - problem solved".
May I be wrong? I hope!