Juha-Pekka has responded to Grady. I note that Grady is also quoted in the full panel transcript as saying "I actually don't throw away all my models; I keep the good ones, the ones that represent the significant (costly to change) design decisions."
I do that too. But as well as keeping them, I generate code, Xml, schemas, validations, config files, installation scripts, tests, and other semantic artifacts from them. This gives a powerful way to co-ordinate different aspects of the development process. Simply keeping them as documentation invariably results in them getting left behind as the code evolves.
Indeed, right now I am working on a change to our DMDM ("domain model domain model") to capture architectural decisions we are making about managing the relationship of serialization schemes to domain models. We generate several artifacts from this model, which acts as the core of our specifications. I have a UML copy of this model in Visio, but I think I'm going to move it to the "obsolete" folder - it is too much bother to keep it up to date.