Hide or not to hide the system tray in a Windows Phone 7 application?

Transparency and colors are now possible with Mango by setting its BackgroundColor and Opacity :

shell:SystemTray.IsVisible="True"
shell:SystemTray.BackgroundColor="Transparent"
shell:SystemTray.Opacity="0"

I would say by default show it unless it really gets in the way in a way you can't workaround, especially if its an app and not a game.