Upgrading 2.4.x "over the top of itself" will replace default files such as the canned system prompts and web pages. If you are using a 'quiet' prompt set, you may need to re-apply the quiet prompts after an upgrade.
The Unity database will be left intact -- there is no need to reprogam any subscriber information or rebuild call handlers. In an upgrade, existing entities in the system will retain their programming.
If you actually uninstalled or removed Unity, you would need to re-install and re-import your subscribers, but that would be treated as a new install anyway, not an upgrade.
Scott Morgan
Cisco Systems TAC
