It sounds like they're running the WP7 apps in a compatibility box. Is that right? One issue developing for Android is the huge API sprawl. Android has this immense surface area of public API now, and they only add new methods and classes every release (I'd love to know how the framework engineers on Android feel about this, because it certainly detracts from the app development experience...). So a compatibility box sounds like a good idea in that case, though making everyone rewrite their apps isn't a good idea...