If you notice in the recent Windows Phone 7 with Mango commercial from Japan, you will realize that the logo for Windows Phone is no longer round. It is now a square tile as shown below.
I think simple logo is better. And it fits well with the Metro UI (Square Tile) look. As mentioned earlier, the commercial that was released in Japan has the latest logo for WP7. Here is a screen grab of a 3D one.
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