I've had crap speeds with Slingshot ever since they introduced their "all you can eat" plan.
Speeds for torrents are no faster than about 30kb!
Decided to try out a VPN proxy to see if that would work any better. And it does! Now getting constant speeds above 400KB which im much happier to have than crappy 30KB/s....
http://hidemyass.com/vpn/ Its not free but its worth it. Makes your broadband much more useable especially in Slingshot free download time late at night. Highly recommend it.
Easy to set up and use.
You wont pick up the Slingshot torrent proxy with it but I havent seen that latch on to torrents in at least 6 weeks.