I’ve just upgraded to WordPress 2.0 and so far, so good. The upgrade process was well documented and went without a hitch. All my existing plugins continued to function. However, as stressed in the documentation make sure you backup your installation and database first. I do regular scheduled backups of my database using the WordPress Database Backup plugin by Scott Merill. It backs up the database and emails it to me nightly.
I’m still playing with the updated admin interface but the main change I’ve noticed is WYSIWYG editing when writing posts, which is a welcome improvement. There are also some nice touches with the post preview and file uploads. This is only my first post with the new version but if you run your own WordPress server the upgrade is worth checking out.