I've just spent the last few hours wandering around the various "open source" analytics programs trying to find the exact right fit for what I want. I'm not finding it, which means that (headache ahead) I may have to write something myself. There's a django-analytics placeholder in GoogleCode, but it's empty. I at least have a model!
Basically, I have a distributed subscriber/producer package, and I want to be able to present individual producers with analysis specific to their work. Because the work is long-form text, I want to be able to tell the viewer that the reader scrolled every paragraph into view (no, really!) and actually read the work, not just scanned it. Both of these are more or less beyond the province of Piwik, Google Analytics, or OWA.
Time to put the research aside and concentrate on finishing the product.