I played a bit with e4Graph early this morning to store some XML documents.  eGraph database files were about 1.5 times larger than the XML files.  Not bad although I suspect there is some room for improvements since XML files compresses well.  The good news is that every elements and attributes in the XML file are stored as nodes and vertices of a graph.  Cool.

The bad news was that it was somewhat slow in converting XML files into a graphs.  But it should be just fine for most client-side applications.  I am going to test node insert, query, and navigation performance later.