I'm using Keen to power the customer facing analytics of my site GetSharey.com I needed a solution that I could get up and running quickly and I didn't want to host my own analytics data. I looked at a number of solutions and settled on Keen. It was setup to start capturing data in about an hour. The visualization library made it easy to add customer facing dashboards too.
Pros:good pricing, easy to setup and use, great documentation
Cons:none