What are your 'best practices', particularly with #2 and #6?
on #6 Android has support for a limited range of display setups, making it fairly easy to provide different UI resources for small, medium and large screens. If you want to start supporting different aspect ratios (the Droid is a good example), you have to either start detecting resolution at runtime and modify layout accordingly, or make sure you build your layout in such a way that it will adapt itself to the aspect ratio. The later is preferred, but always needs extensive testing (hopefully on real devices) because every minor OS version messes up something (1.5 has problems with PNG transparency, 1.6 with 'center' positionings, etc...).
Or, at least that's the reason my friend gave for not developing an interface beyond the default UI for his app.
We could do with a good GUI for designing interfaces, but it's not horrible once you grok the layouts work. Google have acknowledged publicly that the current UI builder in Eclipse isn't good, but there's no public schedule that I'm aware of for when that will be improved.
Thanks for the clarification.