When coding for Android, you have to anticipate that your app might run on different screen sizes and different input methods. All of these are abstracted in the API so you don’t have to fight with hardware-specific issues (drivers & co). I think it’s really not an issue, at least not more than designing a Swing UI for different OSes and window sizes.

In my point of view, designing an app which runs on most configurations only require good knowledge of usability concerns. You know the constraints beforehand, so you have to design your app accordingly.

Sure, with the iPhone, you know exactly where your app is landing… this is one of the benefits of a locked platform, developers can hardcode more things.

Before the iPhone, you had to fight with J2ME or many other specific development libraries (mophun…), and having a single J2ME app running correctly on different devices was quite a nightmare.

At least, Android leverages Java programming knowledge which is quite widespread and the dev kit is usable on ANY operating system. This is the best opportunity so far to develop a single application which can be used with minimal tests (greatly helped with the polymorphic emulator) on a large number of different devices from different manufacturers.