I second habskilla, was getting full speeds with Thundernews but all of a sudden i couldn't get more than 300k. I submitted a ticket which was closed with resolution of suggesting I change ports/check with my isp. After 3 days of running tests I determined they were the cause and escalated the original ticket. When 24 hours went and they didn't respond I created a new ticket and openly asked if they were throttling, that question resulted in my account being closed. Signed on to a new provider and hit max speeds with No problems (2weeks so far).
So yeah, they throttle. Drop them ASAP.