Postel's Law
Theres just no nice way to say this: Anyone who cant make a syndication feed thats well-formed XML is an incompetent fool. - Timoth Bray on ongoing
I'd like to chip in on this with a couple of hard numbers. Depending on your library support, it is possible to write a basic OPML parser in around half-an-hour using an existing XML parser. I've done it twice now, once directly using a SAX-like XML parser and once with a home-rolled XML<->object library; it's easy. It's even a good way to learn how to parse XML because of OPML's essential simplicity.