Has anyone used The Window RPG system located here: http://www.mimgames.com/window/? Im looking to start up a modern era supernatural type game using this engine and wanted to here any feedback on limiting factors of the engine. What works and what doesnt?

I have used the system before (and I'm currently playing in a game that uses it). The system is fabulous and is a great alternative to straight free-form, allowing the storytelling process to go unhindered, while still giving some boundaries to the players.