Well, I took the plunge. Been using the nightlies on a new site for the last week.
Last night I copied a production site of WP1.2.2 and upgraded it.
To prevent problems, I first deactivated all plugins on the 1.2.2 site, removed the files, copied the new ones and ran upgrade.
In about 30 seconds, the site was upgraded and no one knew what hit them!
Great work to all!!