Google’s benchmarking part is now live in Google Analytics. If you opted in to the live, you will find it in your site stats routing at Visitors -> Benchmarking. You will then see a number of charts from sites of similar traffic, so that you can find out if e.g. your visitors stay longer on pages than average, or if they visit more pages than average. Your own site’s traffic will be displayed in the usual blue, whereas the traffic of all the other similar sites is displayed with a gray line.

Also, a category list on top offers items like Music or Society etc which you can pick from to confine the charts to compare to sites within that category only.

The data is interesting to take a look at once, but find it hard to visualize how to develop these numbers on a more regular basis. If you have a site you possibly want to grow the traffic anyhow and not spend too much time comparing to sites of a related traffic size rather, for motivation you would be more interested in what sites in your niche with a much higher traffic might do in a different way.