In case you haven't noticed, I upgraded my web site to Drupal version 6 over the weekend.
The biggest challenge of Drupal version upgrades is making sure your theme and modules make the transition. The APIs can change radically between major releases. That means your add-on components won't survive the upgrade unless their maintainers are actively supporting them.
That's why, for instance, this site is running under a simple, barebones theme. The theme I was using hasn't been updated for version 6, so I had to leave it behind.
As far as modules, only one of my add-on modules wasn't available for version 6—and it's one I wrote myself.
I write a module called category_listing that provides a simple, themed list of taxonomy terms. It's what I used to produce my blog categories page.
The enhanced views module comes frustratingly close to providing this capability. I found two limitations.