Re 64-bit: you are correct. But this still proves my point that Microsoft sometimes deliberately breaks backward compatibility.
Re bugs across different OS versions: your initial comment implied that, because Microsoft puts so much effort into backward compatibility, that app developers do not have to worry about testing across different Windows versions. This is wrong. Just like on Android, Windows developers generally need to test across different Windows versions for bugs, etc.
In other words, my point is that both Microsoft and Google put a similar amount of energy into maintaining backward compatibility. Therefore, Android development presents a similar challenge to Windows development to developers who care about compatibility. And in both cases, the challenge is not that huge... Case in point: the vast majority of apps written for Android 1.5 will run just fine on 4.0 --this trumps all arguments!
Re bugs across different OS versions: your initial comment implied that, because Microsoft puts so much effort into backward compatibility, that app developers do not have to worry about testing across different Windows versions. This is wrong. Just like on Android, Windows developers generally need to test across different Windows versions for bugs, etc.
In other words, my point is that both Microsoft and Google put a similar amount of energy into maintaining backward compatibility. Therefore, Android development presents a similar challenge to Windows development to developers who care about compatibility. And in both cases, the challenge is not that huge... Case in point: the vast majority of apps written for Android 1.5 will run just fine on 4.0 --this trumps all arguments!