Hi Mahendran,
I am happy you like the product!
Regarding the XML export, there is no need for it since .screen and .story files use XML format already. I plan to add a User Guide section for it but for now there is no documentation.
I suggest that you look at the source code for .screen files to see what the XML format looks like. It might help you to know that this format is backed by an EMF model which is bundled inside the com.wireframesketcher.model plugin. In other words the format has clear rules behind it. I just need to schedule some time to translate the EMF model into a human readable user guide.
19 Jun 2010