Supporting different mobile specs (OpenGL)

I want to deploy for iOS 2nd gen and upwards, and various Android devices. That means supporting OpenGL ES 1.1 and 2.0 on different devices.

If I select OpenGL ES 2.0 in the build settings, and build the package, and I deploy it to a device that only supports 1.1, will it seamlessly scale back to use only 1.1 features? Or would it be slow / artifacty if I didn't explicitly build a 1.1 package for a 1.1 device?

If I do need separate packages for deployment, how do I reconcile that with deployment via Android Market the AppStore?