The WP7 app will give you the option of having a live tile for Weatherbug on your home page that will display current conditions of any of your city locations. The live tile is updated with push notifications that includes alerts/badges for serious weather events. Tap the tile and you launch the full application.
The Windows Phone 7 Weatherbug app utilizes BING maps with layers to show animated weather patterns. Weatherbug also lets you tap into local weather cams. All in all, Weatherbug for Windows Phone 7 looks really good.