bad XML

This is still happening. It's because node content is being embedded raw in the xml document. Many nodes have stuff in them that hoses xml. For example, this: </channel>. In effect, you're doing the same thing wrong that our on-site RSS feed generator does, or did, as discussed in rss feed corrupted by certain nodes.

I'm also sad that your cache of pm nodes never gets updated. This means you never catch changes such as nodes getting retitled, moved to another section, or reaped.

It also appears that you don't feed certain nodes, or types of nodes. For example, the Monastery Gates is not fed at all.

Update: It also appears that prlmnks.org stopped updating its node cache from PerlMonks in October of 2006.