Its not exactly as you describe. The android support is just like the IOS support. You have to rebuild your app for it. Still pretty neat, but it is a recompile.
Here's more info: http://www.slashgear.com/video-project-astoria-microsofts-an...
Here's more info: http://www.slashgear.com/video-project-astoria-microsofts-an...
It seems to me that you don't have to compile your app in Visual Studio, though? The video on the Project Astoria page shows an Android app being built for Windows Store using Eclipse on a Mac.
That's a key difference compared to the iOS support. To port an iOS app to Windows, you need to build it in Visual Studio. To port an Android app to Windows, you use your existing toolchain and just produce another .apk with some different dependencies.