its depends firstly on your connection speed but mainly it depends on the site maximum allowable download speed which is being set as a certain speed for free members and another speed for premium ones.
Friend, my internet speed is 512 kbps but I get usually less than 10 kbps download speed when I download torrents. I don't know how to find out download speed of rapidshare or any other downloads. If you know, please let me know.