That's what they're calling the new MS operating system for smartphones. I've skimmed a coupe of articles on it and immediately noted two things.
1: The interface appears to be borrowed straight from the Zune HD. This is not surprising since MS announced that Zune functions would be coming to the Windows phone platform. I like the Zune HD interface and this move should be good for both camps.
2: Some of the changes seem to be straight out of the Apple playbook (with some modification). For instance, "Tighter control over the phones with a minimum hardware definition for handsets to provide a consistent design experience for the user while allowing manufacturers and operators some flexibility to customize the handsets without changing the underlying core." (source: The Mobile Spoon)
Will this still be a Windows phone? I think so. I think we'll see that it borrows a lot of concepts from the iPhone that work and fit well with the Windows Mobile experience but the operating system won't be an iPhone clone with a Windows logo on it. What will be different is that developers will have to modify their applications for the new environment. how drastically remains to be seen. I am hopeful that many of our favorites will stick around.