At this point, I have <2% users on something < iOS 4.3. I have 0 users < iOS 4.0. There are a few users out there I'm sure, but it's so small of a number as to not be worth supporting as either Apple or as an app developer. 95+% are on 5.0 or better, and I'd be willing to bet >80% will be on iOS 6 in the next month. Supporting iOS 3 at this point is silly.