I've been using WordPress for a little less than a week and I really like it so far. Super easy to install and configure. Really nice looking dashboard with everything organized well. Adding plugins a breeze and changing themes simple. And the fact that there's a living breathing active community of developers and theme authors out there is really a breath of fresh air.
What Plugins I'm Running
Akismet – because who likes blog spam really?
wpuntexturize – because WordPress unhelpfully turns single and double quotes into some unicode nonsense. Stop that. This plugin stops that.
WPtouch Mobile Plugin – to make your site look relatively sane on mobile devices.
Limit Login Attempts – does what it says on the tin, helps to prevent brute force login attempts.
I also had the Movable Type importer installed for a bit but obviously that's a use once and delete kind of plugin.
What's Not Running WordPress
For aggregating online activity, I've yet to find anything as nice as MT's Action Streams plugin. So much so that it's still running in cron driving my stream page. So I can't quite say that I've completely replaced Movable Type yet.
What's Not To Like
There's something to be said for the speed of serving up static HTML. Out of the box WordPress dynamically serves up your pages each time a page is visited, so it's a little slower than the old Movable Type site. I suspect I'll get used to that in time.