I'm installing Movable Type to see if it'll be a more user-friendly journaling system (for a nontechnical friend who wants a journal) than my homebrew system. So far, it seems really really cool. All these features that I've been vaguely considering adding to my system for ages (like the ability to save drafts and preview before posting, and the ability to mark entries as belonging to a particular category) are already built in, plus a whole lot more—and, of course, the resulting journal is much much prettier than my system.
If I had known about Movable Type back when I first created my journal system, I would've used it instead of building my own. I don't regret building my own—I learned an awful lot about PHP and MySQL, skills that were directly relevant to my day job at the time and that led directly to my creating the SH submissions database, among other things. And I later learned a lot about CSS from applying it to my journal, which contributed to my being able to help with the CSS for the SH redesign. And so on.
But I gotta say, looking at Movable Type, I'm tempted to see if I can find a way to convert all my old entries to use it. It's so pretty! And so powerful!
(I know there are plenty of other pretty and powerful options, especially the most excellent JournalScape. I'll also be pointing my friend to that as an alternative. But it looks like MT allows multiple users to post to a single journal, which is something that would be useful to my friend, and that would take some time for me to implement in my system, and that I don't think JS has yet either.)