Nelson:
Please excuse my ignorance operating Tor relays, but if I run an exit node on Windows 7 and use something like Peerblock and correspoding block lists of P2P sites, wouldn't this be somewhat effective in stopping this sort of undesired traffic on Tor?
No. If the relay says it will deliver a connection in its exit policy, it has to carry it. Otherwise, it will give erratic behaviour on the client side and this is bad. The relay should be flagged BadExit by the authority operators.