I successfully upgraded this site to WordPress 2.0 last night. It took me about 15 minutes, but most of that time was for doing back-ups. Following the instructions in the Readme that accompanied the download was a breeze. I don’t have many plug-ins installed, and all had been verified to work with 2.0. I simply deleted everything in the root (except for .htaccess), wp-admin, and wp-includes, and uploaded the new files. After running wp-admin/upgrade.php everything was set.
I was going to post the things that I noticed immediately, but someone else already reached the same conclusions.