Upgraded to WordPress 2.0, easy-peasy. No messing around with the template required, same old "backup everything, I said BACKUP, deactivate plugins, delete files, upload files, reactivate plugins, smile contentedly" routine. So long as you keep up-to-date, the upgrades are a breeze.
Love the new live preview thing, where you see the post as it will appear on the site, and the nifty collapsible bits on the "Write post" screen. All my plugins seem to work, and password protected posts may come in handy. Well worth the upgrade. Sehlat, did you spot the blog vanish in the five minute upgrade window?