Just seen your post.
Our sipX integration got stalled with other, more critical fish to fry. As, frankly, did Zimbra development - it just wasn't flexible enough (at the time) to do what we needed it to do, and our users just couldn't get on with the web interface. We're now revisiting it, but our focus for the moment is to get a generic version of the "toaster" sorted to integrate Zimbra with another (industry-specific) open source project.
sipX is still on the back burner, and we'll certainly come back to this. The other app also supports click-to-call, so we'll have to start with making a decision as to what we do - Zimbra or not. If we use Zimbra for the calling functionality, the "toaster" will be needed to translate clicks elsewhere into Zimbra calls.
Ho hum, so many decisions, so many variables, so little time :-)