When we left our story last time, things were in decent shape. But then I noticed that some of my img_assist tags weren't displaying, and had to meddle with the custom img_assist filter some more. I made some progress, and I feel I might as well share.
After some deliberation I decided that it was finally time to move to Drupal 7. Most of the modules I use have been ported, and I figured I could hack my way around the rest. While there's substantially more hacking to be done, I have a fairly good handle on it so far. There were more complications than I expected, however.