Ok, so I know that I bash Apple enough. They drive me crazy from a tech company standpoint because they often copy what others have done, make it a little better, and then release it like no one has ever done it before. However, despite that I'm still a nerd at heart which means I like all forms of computing devices. I've been doing some iOS development recently and here's something I came up with if you're trying to decide if you should still support iOS 5.
iOS 6 seems to have a number (197) of security fixes that were never patched in iOS 5. Check the wiki to verify when the different versions were released. This is just iOS 6 not 6.1.4 and everything in between or iOS 7 currently in Beta 3.
According to this study, as of June 7th iOS 5 only had 5.5% of the iPhone market share as opposed to 92.7% using iOS 6. iPad is similar but slightly higher at 13.4% vs 82.9% and those are most likely left over from the original iPad.
Finally, the part that was most important for me from a development standpoint is that iOS 6 introduced Collection Views, UI State Preservation, and Auto Layout.
Collection Views were something I was considering using for part of the layout and would need another away to implement if I couldn't use them.
UI State Preservation is a feature that would greatly reduce development time.
Auto Layout is probably the most important feature for most devs. It will greatly reduce the development time needed to make sure portrait and landscape are working and look similar. Here’s part 1 of 2 of a rather in-depth example of the differences.
My personal recommendation would be to drop support for iOS 5. With the way Apple forces upgrades and iOS 7 on the cusp of being released it only makes sense to look forward. However, if you do decide that iOS 5 is important for you to implement, then look into this open source implementation of auto layout. There’s also a link in there to his implementation of a collection view. Update: NO WAY!!