Resetting your IP does have an effect on your internet speed. But maybe the reason for it is a bit hidden. I am no IT expert, but this is what I have experienced.
Using a firewall (like ZoneAlarm) you can see how much internet traffic to your PC is being blocked. For those of us using P2P aplications, your shared files are assosiated with your IP, so people around the world that were put on hold to download from you, will ping your IP till long after you have shut down the p2p software. After a few hours of trying to download a movie or whatever, there are so many people trying to get data back from you your connection slows down to a crawl. If you open ZoneAlarm and check the blocked traffic, you most likely will see about 2-5 incoming connections per second being blocked! Resetting the IP immediatly stop all the incoming connections and your internet speed is back to normal.
Atleast this is my experience, while I stayed in Germany and frequently downloaded stuff via p2p. All p2p downloads are not illegal though, since major PC game companies also uses this method to distribute patches faster.
There may be some other reasons as well, but will leave that to the IT experts to share.
