Yes, a number of people at my company (with about 1000 people in it) tried to spread usage of it, but it only stuck with about < dozen people. Communicating through status messages doesn't really seem to give enough detail to anyone who needs to know.
I'm not sure what you mean by communicating through "status messages". It doesn't seem like a good way to operate. Posts are not limited in the same way as Twitter messages. You can add various attachments, and create messages longer than 140 characters. In most companies email is the dominant form of communication and other tools (including discussion boards etc.) just don't get uptake because people drop back to email.
In very big companies (> 20k) there is more of a need for a tool that that can connect people in different "silos". I've seen how Yammer has helped people in this type of organisation.
