I just installed WordPress 3.0 to run this thing, and as always since the later 2.x versions came out, the upgrade was silky smooth. The biggest change is the integration of the WordPress MU function, which allows multiple blogs to run off of one installation. It seems from the WP Codex that most of the highlighted changes are back-end upgrades with better hooks for developers, as the dashboard interface looks almost identical to the late 2.x versions. There are some new features, like the easy creation of custom menus and headers, and the most visual change is the adoption of the new Twenty Ten default theme.
My big hope is that WP is moving in the direction of a direct competitor to larger-scale CMS products like Joomla and Drupal — as this BusinessWeek article notes, the user-friendliness of WP (both for users and developers) is the differentiator. Let’s hope!
And on a totally unrelated note, this is a grouping of two awesome dudes.