Yeah, I'm not up to speed on Android. But, so, that only accounts for 3% of the users. It still means only %5 are on ICS, and the rest are basically on 2.3.
So the process for developing a new iOS app today is:
Pretty much, yes. New features in ICS need to be viewed as optional and probed if you're going to use them. Though to be fair there really aren't that many you'd really want -- ICS focused more on the core apps and user experience than it did on extending the platform APIs.
Also, my memory is that something like 20-30% of iOS users weren't on 5 yet. Is that wrong?
About 80% of users are on iOS 5.0+, so, 20% are < 5.0. But the 20% that are < 5.0 are not the ones that will be downloading and installing fancy new apps. If they were big app consumers, they would update the OS.
The iPhone 3G is stuck on iOS 4.2.1. When I still had my 3G, I happily bought apps if they still ran.
We also had quite some support requests for a three digit dollar app (!) because customers never bothered to update their iPad, the OS versions were all over the place.
The compatibility library gives a developer a lot of pieces from the latest versions of the SDK that one might wish to use. Also ActionBarSherlock (http://actionbarsherlock.com/) is an excellent library that will allow one to create solid looking apps using Fragments and the ActionBar on older versions of the OS.
So the process for developing a new iOS app today is:
For Android, it seems to necessarily be: