Just wanted to tell you about a successful upgrade from WP 1.5.2 to WP 2.0 RC-1.
System: My blog resides at an ISP ( web hotel ) running Apache and MySQL. This is how it went:
1. Unpacked the distribution locally.
2. Copied the database connection strings from wp-config.php to wp-config-example.php and saved it as the new wp-config.php.
3. Deleting everything from my blog except the themes and plugins I've added.
4. Uploaded the new WordPress bunch to the server
5. Reached for the /wp-admin/upgrade.php from my browser
6. Clicked the link Upgrade WordPress>>
( After getting an introductory error message "WordPress database error: [Table 'petitpub.wp_usermeta' doesn't exist] - SELECT meta_key, meta_value FROM wp_usermeta WHERE user_id = '1'" )
It all worked like a breeze, including my themes and user and my permalinks.
I'm happy :-)