There's still some holes here. The simplest exploit with the config given is just to get your ISP server logs: if you don't use dns caching they'll still know every site you visit. If you set privoxy to forward dns requests all you're doing is sending the packets out to tor, which encrypts the traffic and sends it hop to hop only to send the dns request right back to your isp. It would be trivially easy to correlate these "alien" dns requests with your outgoing traffic.

If you want to be anonymous make sure you don't use your isp's dns configuration; set your dns resolution to the public dns hosts scattered across the globe.

Oh, and don't forget this doesn't "protect" you on gaim or usenet or email unless you also set those clients to use the socks proxy provided by tor.