Your internet provider MAY throttle torrents.
Your connection may be WIFI which gives you much less speed than wired.
There might not be many people with the file you want
You might be using the net at the same time for other things
Your processor / RAM and ethernet port / wifi affect speed too.
When im downloading linux iso's i usually hit about 4mb/s and when downloading things like red hat it can hit 7mb/s in bursts and rest out at 5mb/s Dunno bout other files cuz i only use linux distro;s.
Check the most recent comment about the speed. If the last comment is old it may be a dead torrent, but the ISPs are throttling back torrents. The OS or Torrent client should not make any difference.