Moving through the presentation, Google showed us that Ice Cream Sandwich has a very simple, clean, tile-based interface. There are no rounded corners, no brushed metal textures, visual contrast is very high, and most of all, content is king.Sebastian Anthony
I know that despite how others might feel about the platform and its usability, the first thing that many people thought about WP7 when they first saw it was: 'Man, that looks stylish'. Google, intentionally or not, has given a nod to the Metro UI style's legitimacy. Google's new "Roboto UI" as it's called, is also imbued with some Google+ DNA to maintain interface recognition.
The other good news is that Android 4.0 is indeed open source after 3.0 was not.