It won't work immediately upon installation, you need to provide an API key. I used Firefox; in the Add-On Manager, look at the Details tab of the plug-in. The instructions are fairly straightforward, I had it running in a couple of minutes.
Edit: The plug-in may need a refresh of the YouTube page to work.
If you think g00g is going to allow you api access to the stats of someone else's content, I have a bridge to sell you.