For me, it's much more than the aesthetic, an application's window must work the same as the host OS. This includes windowing controls, context menus, and things like Aero Snap. Photoshop is a big violator for breaking Snap. Chrome (the browser) is out because
I hate not having (window) chrome to grab on to. Zune gets partial points for obeying snap, but instead of allowing the OS to show the transparent preview of a Snap operation, it immediately reflows the application. I'd rather have the consistency.
I like the Chrome, and think Expression Blend lead the way, even though there is no placating you, hence, I know not why I bothered to post.
It is differentiated UI, casting away "prior art" and giving designers complete control.