Ah, the mythical enterprise. I've yet to see an example in which UML Class Diagrams have been useful, but whatever, I guess that's the same enterprise in which you've got "architects" outlining stuff in UML, then passing that to the monkeys to fill in the blanks.
I find UML Class diagrams useful for a one-look document describing the overall architecture of a piece of software. Where they are weak is that you really do need a couple of paragraphs of plain English describing each class as well, and there's not really anywhere to put that on a UML Class diagram. The other really useful diagram in UML is the sequence diagram. If you write out the Sequence diagrams for a few key processes in your software, you've gone along way towards giving a roadmap to people that need to get in and modify the code. These are both documentation use-cases though. Using UML as a design tool (other than very informally on a whiteboard) seems wrong to me.
