Access/subscription split of friends is one of the biggies, I think. Cut tag expansion is really neat, too, as is being able to preview with spellcheck without getting a faceful of raw HTML.

I think my favorite aspect of Dreamwidth, though, is that how user-centered new features are (and I am so excited about the upcoming changes to the update page). When new things roll out, they're things that I've seen discussed in update posts with user feedback taken into account. This level of "Yes, we're really listening" hasn't been my experience on other journaling sites.