Fairly well being the key phrase—it's not difficult for a determined individual to bypass.
Look at all the software that exists to help pirate stuff, the dozens of seedbox companies, the hundreds of trackers.
I'm doubtful it would have a big impact. The knowledgeable would slap a VPN on their PC or buy a seedbox. The less technical would wait for Deluge or Transmission to add a VPN panel to their settings screen.
I'm fairly certain things would go back to normal pretty quickly.