In the new exporter, when the option to export only the subtree is specified, the first heading in the subtree is used as the title of the document. This seems wrong, as it becomes the title, the first element in the table of contents and the first (not necessarily the top level) section in the document.
When the document is explicitly narrowed to the subtree, or the subtree is the selected region, the #+Title: attribute is used for the document title, which seems to be better. Arguably, using the subtree heading for the title would be the most logical solution when exporting a subtree -- in my case that would usually DWIM. rick