Only using 2.2 APIs at this stage would only hurt the development of your app. Targeting 4.1 and using the support package gives you full access to Fragments and Loaders while still supporting the older SDK versions.
There's also the ViewPagerIndicator library.
Jake Wharton really has done the Android world a massive favour.
Though looking at developer.android.com it does seem that it would be safe to target 2.3 as a minimum.
http://developer.android.com/about/dashboards/index.html
Unlike with iOS where it is easier for users to upgrade their OS if their phone supports it, Android version upgrades come most often when people upgrade their phone and that means at the end of a 2 year contract for most people.
Targeting the most recent Android version seems like a poor way to get people to use your app.
Sure, if you target 4.1, you can't necessarily use every single new feature in Android on older devices. However, from a design/UI point of view, Android's backports of many new features (and projects like ActionBarSherlock) such as the action bar means you can design for 4.1 and have the code work with many previous versions.
I agree with the grandparent post: design for 4.1 and set 2.2 as a minimum. In cases where you want to use new APIs, you can use conditional classloading techniques.
Read: http://developer.android.com/guide/topics/manifest/uses-sdk-...