You bet! I spent 3 years of my life consulting with these folks, helping with architecture, coding the network and voice components, recruiting for the UI and server-side.
It started being useful two years ago. We were our first users. Our productivity climbed, and our travel bill halved immediately.
Its nothing like Skype. No "phone call" model at all. You're instantly connected, can see everybody in your group at all times, you can tell who they're talking to, when they're done.
The map feature is more useful than it might seem. You can tell what your team members are doing, who they're talking to, whether the staff meeting has started, if Bob is in today etc.
I didn't call out my involvement this post, I've done that on half a dozen posts before, sorry.
http://www.linkedin.com/pub/joe-altmaier/6/38b/996