Whilst searching for an outliner in preparation for a largish project (which I won't discuss yet), I stumbled over a small native Win32 program called The Guide. I love programs that just work, and this one does just that. The only downside is its export function, which is limited to exporting RTF. I've already contacted the author whether he would be able to add an XML export for me, and he will, time permitting. A very useful small tool.