Edit: That is, from iTunes Connect. Maybe your pals use some sort of usage logging/statistics from within the app.
The biggest gains for me have been:
1. when I could discontinue previous OS version (3.x) support because most of my users had transitioned to 4.x
2. It lets me know which features my users are actually using so that I can focus on enhancing and refining them.
3. It lets me know how many installs vs. sales that I have. And yes, this includes any pirated copies.
Edit: That is, from iTunes Connect. Maybe your pals use some sort of usage logging/statistics from within the app.