I was planning a post discussing this topic, but it looks like Lars Trieloff beat me to it with his post on DocBook vs. DITA.
Now that the DITA TC has approved the 1.0 version, it seems to be gaining quite a lot of momentum. Our (Flatirons Solutions) CTO, Eric Severson, spoke at the Content Management Strategies Conference, where they had 14 presentations on DITA related subjects! See http://www.cm-strategies.com for details.
I plan to get a lot more involvement in DITA in the near future. Perhaps you will see a new "DITA" category on the blog.
See also: DocBook