Somewhat unusually, Microsoft has allowed a Windows Phone 8 simulator into marketplace, which allows one to practice the perfect arrangement of their start screen before Windows Phone 7.8 and 8 arrives in the next few months.

Using the app you can practice resizing tiles and imagine where you would place the new small icons, and of course also see what a full-width start screen will actually look like on your phone.

Of course the app can not actually launch 3rd party apps, but it does pull in the icons from Marketplace, and even initiate the download of apps for real.

The app is free and can be found in Marketplace here.

Via MobilityDigest.com