If you care at all about quantifying your traffic (and who doesn't) then I cannot recommend this extension enough.
Installing is a little more complicated than many extensions. In fact, any extension download that tells you to "unzip first" means that you're should be a Joomla expert, but if so, then the process is otherwise rather straightforward.
I have found this to be a good complement to Google Analytics, even with Google's new real time tracking. However, you do need to be careful about how much data you want to track, because Joomlawatch will make your database bloat up something huge. This becomes an issue with migration and upgrades, which in this case, are still anything but intuitive. Knowledge of MySQL is essential.
Nice work, though. I can't recommend enough.