Actually my opinion comes from not the OS itself but its functionality. The design of using tiles, to the only about 2,000 apps available, to not being able to have its own MicroSD & others like wallpaper on home screen will throw some ppl off.
Now im not a hater of Windows Phone 7, I will be one of those who probably purchases both HD7 & Venue Pro because I like all OS's around like the iPhone even. I want Symbian, MeeGo, Maemo, Blackberry, Windows Mobile/Phone, Android & iOS. Hell even give me OPhone=China Mobile/Android Type. I played with it last nite. Remember, I used to be teased here cuz I was supposedly a Microsoft fanboy. However, at that time Windows Mobile only supported what I wanted. But now almost all of them do.
Also may I add that business e-mail functionality is not all there like Windows Mobile had so many businesses may not transition over depending on their needs.