It's been great fun to get back into writing in DocBook format. As a geek, any book that has a makefile and that you can keep under sensible version control is heavenly. It takes me back to the joys of writing Code Craft. I wrote that entirely in DocBook, and it made my life much, much easier.
But then, I'm a geek. So perhaps it's a perverse kind of pleasure.
Microsoft Word (or Open Office, or Apple's Pages, or whatever) are great tools for the great unwashed, but if you're writing any kind of technical documentation, or if you want a programatic degree of control over your document, I strongly suggest you try out DocBook. It's not for the feint of heart, but it's a very rewarding writing technology.