Chances are, I’ll back up my database, etc., tonight and give the upgrade a try. If the new theme breaks, I’ll go back to the old one. If the whole thing breaks, there will be weeping, gnashing of teeth, tearing of hair, and rending of garments.
Then I’ll just revert back to the old site.
Update: Victory! (I think.) The upgrade seems to have gone off without hitch. I grabbed the new version of the theme, and customized it a bit, updated a few plugins, and after a bit of tweaking I had a blog again. I’ll have to kick the tires a bit before I have any serious critique of WordPress 2.0, but things look good so far.