Things that are not yet supported (Win 8 app store):
•Network classes, WWW is supported though
•Animation on script variables
•AnimationEvent callback functions with arguments (you have to provide a function with no arguments or with AnimationEvent argument)
•GameObject.SendMessage (partially works, but function which accepts the message must match the message sent, because the argument conversion doesn’t work)
•Fog doesn’t work on devices with feature level < 9.3, you need to implement it manually, see http://files.unity3d.com/tomas/Metro/Examples/MyCustomFog.shader