I’m part of a group of quantitative UX researchers at Google, and we like to think of large-scale usage data analysis as just another UX research method. We’ve developed a couple of useful methods to help choose and define appropriate metrics that reflect:
For an introduction, start with my blog post for Google Ventures, How to choose the right UX metrics for your product. You can also check out this animated explanation of the blog post.
The academic reference is Measuring the User Experience on a Large Scale: User-Centered Metrics for Web Applications, which I wrote with my co-workers Hilary Hutchinson and Xin Fu, for ACM CHI 2010.