developer Nick Farina's post about his experience developing on Android after developing on iOS.Are you an iOS developer thinking about dipping your toe into the Android pool? If so, you should read
Farina compares the development environment (he writes that you'll hate Eclipse at first, but once you get used to it "you'll enjoy some seriously amazing, productivity-boosting code completion, refactoring, and automatic fixing."), provides slick side-by-side code comparisons (spoiler: Java and Objective-C look a lot alike) and addresses the fragmentation issue.
Not that fragmentation is unique to Android; it's just exaggerated a lot in the media. We need quite a few iOS devices in our lab too. One tiny unexpected OS or device difference can bring your app crashing down, on any platform.
It seems that, once you get used to Eclipse the two platforms are pretty similar. The big differences are testing environments (though both end up requiring physical devices to do real testing) and the UI libraries. Android's XML-based UI tools make for much easier development, even though it's just one more thing to learn. But Apple's GPU support makes for much smoother animation.