I'm rather disappointed in the use of generic variable and/or constant names in 1.5. In particular, the constants (DB_USER, DB_PASSWORD, DB_NAME, DB_HOST) used for database information in wp-config.php. This is a poor programming practice at best, and is almost certain to cause problems with a significant number of users. If I'm not mistaken, this practice is specifically warned against in the coding guidelines for plugin developers. Please change this in future versions. I have already run into this problem in upgrading a site that I do not have the option of changing constants that are previously defined for other areas of the site.
Otherwise, you guys rock!