1. Should probably also prompt for a hostname, rather than defaulting to 'localhost' for support with remote MySQL servers.
2. Would be really spiff-taculous if it automatically changed the settings.php file as well -- this means it would need to prompt for a $base_url, and use some fancy regex action to replace the $db_url and $base_url variables.
3. Finally, use Drupal's multisite features to prevent conflicts on cvs update... create a directory called domain.com[.subdomain] (off the $base_url var) in the sites/ folder and save the replaced settings.php file there.