I launched my app (Finderous) only on ios 5.x becuase 1. I didn't want to support an OS that is already shrinking in usage. 2. It's just a matter of time people will upgrade to IOS 5.x as it is free. 3. I learnt ios programming only on 5.x 4. I found it time consuming to learn pre 5.x programming once I started with 5.x :)