[hiperlink]

(Disclaimer: I'm not UML/architect expert)

I get your opinion from a programmer point of view. However from the big picture point of view, either from the architect or from the client (if she (even partially) gets UML), it could be really useful.

E.g. let's consider working for a large financial institute, designing and/or implementing very difficult workflows / algorithms what would you use instead? In my experience most of the clients don't take the time to read half (if at all) of the agreed spec, not to mention understanding. In that case an activity/state diagram really helped a lot.

And on not versionable: you are right only to an extent (e.g. exported Visio diagrams to JPG...). However there are tools/methods, which can be versioned (e.g. generetaing UML via Graphviz/dot, and AFAIK Enterprise Architect supports versioning too).