[iamchrisle]

I actually use event tracking a lot to track exactly that. For our clients, we not only know which features they're using most but by tracking validation errors in Google Analytics we also know what parts of the app is giving users trouble.

Best part is, with Google Analytics you can see what people did before and after they ran into trouble and correct for the user experience.

[swalberg]

This. We recently started doing this and the data it's provided has been awesome.