There's also StackShare which presents things in a nicer UI. For example, this is Trello's and Stackshare's stack:
I've been looking around for a custom analytics platform that I can pump a load of events into and interrogate later however I want. Of all the ones I've looked at, keen.io looks the most interesting from a developer flexibility stand point, but that's just from the outside. If anyone has experience I'd love to hear it.
We use Keen IO for all our user metrics. Specifically their CommonWeb library https://github.com/keen/common-web, which automatically tracks clicks, pageviews, form submits and a few other actions. Keen has been great for us, particularly because we don't yet know exactly what we want to track, it's constantly changing. So having one place that houses all our events then being able to query that as we see fit and build dashboards (http://keen.github.io/dashboards/) has been really helpful. You can see some more feedback from other people here: http://stackshare.io/keen-io.