Cutts said, "they just rolled out a new (free!) feature that helps you figure out how your users like your website!" "I highly recommend it," he added.
Here is a screen shot of what it might look like on your site:
The reports that it outputs is nice and it is good to get user feedback on your site about your pages but I am sure there are a ton of webmasters who will think - no way am I adding this to my site. Google can then use this data to hurt my web site. Of course, Matt Cutts would say Google currently doesn't use this data for ranking purposes.
Anyway, here are the stats it outputs:
Will you add this to your web site?
Forum discussion at Google+.
Update: As expected, Matt Cutts said they won't use it for ranking: