But to be more fair, in the past MS didn't really change the UI at all -- they just said, here's a stylus. In this case they actually provide a radically different UI.
It's the UI from Windows Phone 7, which didn't exactly light the industry on fire.
No, but I think that had as much to do with marketing and overall execution than it did the UI itself. I have to admit that what I've seen of the WP7 UI looks quite nice, even if it pains me to complement MS.
If they execute properly on this I could see it being a big hit.