Try the Windows Phone 8 Start Screen on your WP7
There's a new app in the marketplace called W Phone 8. It's a simulator for the new start screen. You can resize, drag and change the colors. It works pretty well and looks awesome. Now you can now design your layout before the real thing comes out.
Get it FREE on the marketplace: http://windowsphone.com/s?appid=64fde631-3f99-449d-8149-28e33084dde6