The basic problem is that I didn't completly understand the OPML specification and I started to implement the mini API before I knew more about it. The area that I need to extend in the object model is around the attributes of the outline element. I only thought you had a type and text, but it turns out the specification is quite loose around the attributes that you can have, but there are several well used attributes that hook up with files, links, html and rss etc. I will document them some other time.
Other than that the OPML XML that it generates seems to be good, apart from the quoting of " and the &'s :)