Tygraph is a analytics tool that works with Yammer and Sharepoint (Microsoft products). It gives you valuable insight in data directed from those tools. You can for instance see what posts or groups on Yammer have the most influence and get most likes and comments.
Look and Feel?
Certainly meets expectations, modern and user-friendly
Certainly some conceptual and technical innovations
Easy to implement?
Some effort required
Tygraph is a good example of a Business Information (BI) tool that can be used to see analyse how your Yammer platform is being used. It gives you good insight in the active contributors and most active groups and messages. It is fun to see what messages and people have the highest impact on Yammer. The question is what you can do with that information.
Tygraph is completely focussed on Yammer. There are other examples of BI tools for your collaboration software. The problem with this kind of tools is that it, gives you al lot of information, but knowing how to use the information is less straightforward.