If you want to self host a blog, there are two main contenders:
Now, I'd already decided to not use MODx, as used in the main site, as the blog engine. MODx can function as a blog, and the demo site includes one, but it don't have the expertise with MODx to get as complete a product as two above. I don't suppose I'm much different from most people who set up a blog; they're not specialists, but they want to put their own ideas into it, so they need some guidance on the specifics from the platform they choose. I still don't understand about how trackbacks and pingbacks work! <!-- more -->
Unfortunately, I didn't get on with Moveable Type. I can see that it's a very powerful framework, but I'd never dealt with perl before, so the cgi-scripts caused me some head scratching. After 2 full days of installation, I'd only got it partially working, so unfortunately I had to let it go.
Which left me with WordPress; and I like using it. It runs on php, which I've had some experience with before, and I got it set up and running on my own server in about 20 minutes. I think if it wasn't my first WordPress install, where most of the time was taken up with understanding what it's doing and why, the "5-minute install" is very realistic! It's happy to run as a sub-folder of my main site, and the plugins and themes are extremely easy to use.
So then there's was just customisation. Most of my time was spent setting up the theme and making it match the main site theme. I used the Shape theme from Themeshaper so I started with a structured template that included all of the WordPress specific markups and functions. The Shape theme is also used as the template for the main site's templates to keep the css consistent. A lot of time playing with the css style files, some very minor changes to the theme's php files and a few plugins are all that make the difference between this install and everyone elses.