We're about to get a real world test of two very different approaches to phone OS use - Google's "throw it over the wall approach", and Microsoft's "create a standard" approach:
Each device must feature three standard hardware buttons, for example, and before they can ship with Windows Phone 7, they have to pass a series of tests directed by Microsoft. (As I mentioned in a feature story about Windows Phone 7, Microsoft has created new lab facilities containing robots and automated programs to test each handset to ensure that features work properly and consistently across multiple devices.)
The iPhone has had the consistency thing going for it all along; Microsoft is trying to create something similar across a broad range of hardware vendors. It might help them take the slot Google is in right now, or at least split it with them.