I have reworked the entire system from the ground up, putting it on a much firmer mathematical footing (before I had a lot of arbitrarily chosen constants). It should learn ratings more swiftly, works better with some of iTunes's limitations, and also requires much less effort to install. The documentation has been rewritten accordingly. Please let me know if I missed anything.
The theory section has been removed as it is now obsolete. If there are requests, it will be rewritten.