One of the reasons was I wanted to upgrade Wordpress to 2.1 and I knew that it could take a while. I wanted to make sure there were no problems with plugins etc. But I've upgraded, and I would say that I haven't run into any troubles. Everything appears to work as it should.
He follows this up with some initial impressions of the new version, including the image upload system and the auto-save functionality (to ensure the least amount of data loss, just in case).