I've played with PostRank in the past (probably back when they were called Aide RSS). They're a Canadian company, based out of Waterloo, founded back in 2007 (CrunchBase entry). They're best known for their "PR" - ranking on blog posts to see if it is important. Since this is similar to what Summify is doing with their social news reader, I'm hoping there might be a connection here.
I dived back into it in the last couple of days because I got notification about PostRank Connect, which is a brand / influencer connector / tracker (as near as I can tell - it's not really "turned on" at the moment).
But PostRank analytics is what is live now, and it's great. Here's a screenshot of the front page of this blog, the default "Overview" tab in PostRank:
The top is the engagement value as tracked by PostRank - comments, tweets, delicious bookmarks, and so on that that post has generated. The bottom are page views from Google Analytics - you click a button, do the OAuth dance, and then connect in your existing Google Analytics account.
Most of the traffic to my blog is organic search from being around for 10 years, so you don't see massive spikes of pageviews correlated to engagement.
Here's another screen shot from the "analyze" tab, which shows you a compact view of posts to your blog, with engagement events and engagement points to give you an overview of how impactful each post is:
If you look carefully, you can see that the Twitter and Delicious links are underlined - you can click through and see more info about who has tweeted / bookmarked your posts. I'd like to see click throughs and info for all of them.
You can see more details about the PostRank Analytics service on the tour page, where you'll also find that it is $9 / month or $99 / year, although I've been told that with a "Connect" account, you'll get a free Analytics account.
The Connect / Brand / Influencer model seems to be hot again: when I heard about Boris Wertz's investment in Empire Avenue, I spent some time kicking the tires as well. Feel free to buy some shares in ticker symbol BMANN.