I've been wanting to do this for quite a while, but this week I finally got around to overhauling The Web's Bushiest Site. I've migrated the blog to WordPress and got a spiffy and elegant new theme.
Before the migration the blog had been running on Joomla, which seems to be a capable foundation for a multipurpose site. However, after 15 months I grew tired of its weaknesses as a blog. Joomla forces the use of a two tiered category hierarchy for posts which I found to be almost entirely useless and frustrating. It also has a terrible preview function. I could never know what a post would look like until it was actually live, which meant I often had to publish a post and then edit it several times to fix formatting issues. Finally, Joomla doesn't include comment support out of the box and none of the comment plugins available have a good mix of ease of use, ease of administration, and good visual design.
As for WordPress, the platform is meant to only do one thing and it does that one thing really well. In my opinion the themes and plugins available for WordPress are much nicer for blogging than those available for Joomla. The category hierarchy is way more flexible, and the admin interface is much cleaner and easier to use than Joomla's. Finally, comment support out of the box is great.
Comment on your love/hate of the new blog; I always appreciate feedback.