My office just deployed this as a part of our ongoing migration to a cloud services platform (in this case, Office 365). We're using it for internal communication for both voice and text and are finding it to be reasonably useful. We used to use an in-house XMPP solution but Lync has been a much more polished user experience. There are also iOS, Android and Windows phone apps to allow for unified messaging. That being said, it does lack some features like in-line picture messaging, true cross device syncing and attach to message features. It's quite nice however for its tight integration in to Outlook.
