Ask HN: SaaS analytics - how much do you track?

I have inherited a web app with a bunch of features.

I was hoping to learn more about how people are using analytics to track usage of their web apps.

I'm particularly interested in hearing answers to the following questions:

1) Which services do you use (Google, MixPanel, KissMetrics)? Any recommendations? 2) How richly do you instrument your service to understand individual feature usage? 3) Have you used the APIs to extend the usefulness of the main analytics services?

LJ