I'm a developer currently looking to utilise the XML API feed. However, the implementation is currently bugged; it appears be putting invalid XML data characters in to the data stream unencoded which causes XML readers to choke. The ampersand (&) character seems to get through the most;
e.g. col 341 of line 62 in this feed;
If you open that link in the chrome browser, for example, you'll see an error reported at the top of the page to this affect.