We now expose the internal DataTable called TreeTable and the internal DataView called dvTree. So to debug I can bind these to a simple GridView. For example if I had the GridViewTree called gvtFiles and wanted to debug it, I could add a GridView to my page, name it gvDebug and bind it like so:

this.gvDebug.DataSource = gvtFiles.dvTree;
this.gvDebug.DataBind();

or using the table
this.gvDebug.DataSource = gvtFiles.TreeTable;
this.gvDebug.DataBind();
Jim