Another data source you can use is data from Sparkle. Sparkle is a library that Mac developers can freely integrate into their applications. Once included, it handles the update process in an invisible and robust way. We use this in our programming environment for the Arduino so we can get a sense for who is using our software, where, and when. (Well, that's a side-effect: we use it because it makes it easy for us to provide updates to our users.)
Here are the (limited) logs from our Sparkle framework. There are both Apache-style logs and CSV logs; I'd rather you use the Apache-style.
