Writing Software to Collect Click Stream Stats?

AntiPasto asks: "I am working with a small business that wants to evaluate their "click streams[?]". I've investigated openstats and even commercial products like Funnel Web as being turn-key solutions, but they don't offer the sort of authenticated-user page-view detail that we're looking for. I've since decided to start a mod_usertrack implementation, but it looks like we need to write our own stuff to process this. Anyone have any experiences with tracking a user's visit?"