Nice post. Like it much, really. My projects are usually so rushed that no one takes the time to set up any versioning whatsoever.
One exception: CuddleFish CMS. It is Zend Framework based and has a dedicated DbController that has an action for every db update ever applied.
The advantage? You can use the regular CMS GUI to update the database by clicking a friendly name in a list of actions. From the same interface you are one click away from an install script for the database.
But then, this is highly dedicated. I like your approach very, very much. Anyone who is not using a database versioning system yet should give it a try.