Well, I'm not even sure PVM is the right tool for this job. Essentially I have a tree structure, where each node is a work unit and is dependent upon the results of rendering its children. Advogato is cool. I'd much rather rewrite it to use an XML language to define the jobs first. The job engine really hits MySQL in it's weak spots.
Performance can really grind because of uber-complex queries.
MySQL really needs sub-selects. It's all really trivial stuff, but it works. I need to buy her some flowers. I haven't done that yet. The nicest place I've taken her so far is Macaroni Grill.