[dangrossman]

I use MixPanel for that, and did a pretty simple implementation

* The event-tracking snippet went into the layout template shared by all pages

* The only property on the event is the concatenation of the controller class and method name being executed -- this identifies what screen is being shown

So, basically, one line of code in one file instruments the whole app, and is enough to measure feature usage.

Here's what the resulting trends report looks like: http://i.imgur.com/6Uk8hjQ.png . Obviously, it can be filtered to compare fewer features or broken down by cohort more readbly.