Unless your ISP has started to filter your p2p downlding speed, the speed of downlds depends on your sources/hosts. If you connect to a Shareazaa (RAZA) user for example, they are reknown for offering very slow speeds for others. They use most their bandwidth on other networks that require it. That's what's not good about multinetworking programs.

If you downld from a dial up modem user for example then you'll also get small speeds. Perhaps the host is busy uploading to others & speed fluctuates, etc.

Try an experiment, downld a magnet link from here & see what speeds you get http://www.magnetmix.com/video.shtml
If you get good speeds then you know the problem is unlikely to be your ISP but your sources. If you get a poor speed, then I would be suspicious of your ISP.