Currently we use Wordpress for our blog. The advantage of Wordpress is that is a mature piece of software that does everything we need it to, straight out of the box. The disadvantages are primarily in terms of integration with the rest of the site: Wordpress uses its own users & authentication system, and because it was written with MySQL in mind and has no database abstraction layer, it can't use the database that we use for Django (Postgres).
The database issue is problematic in a very practical sense, because in order to list recent news-tagged posts on the site's front page, we are forced to get and parse the blog's RSS feed! It's a terrible solution, and made worse by the fact that we don't use any caching on the site yet.
There are two main ways I see to improve the situation. The first is to write a Wordpress plugin that saves/updates a copy of each post that is added/updated onto the Postgres database as well. The second (and "ideal") way would be to implement a blog within Django itself. The problem at this point, however, is that there is no Wordpress equivalent in the Django world. Django prides itself on modular/reusable applications, and a sinlge heavyweight solution which does everything is frowned upon. There are a variety of options that seem decent (Django-Mingus is one), but they will need proper investigation.
Of course, the quick and dirty way of improving the situation is just to start using caching on the front page.