That sucks. That is just lame and selfish - did I say it sucks too? Well, it sucks. It really sucks!
Set your host connections to 2 or 3 and uploads (sharing) takes little away from downloads because you only need small outgoing handshake packets to get a file.
Play with it a bit and tune it as you go. You will find that uploads don't slow you down much. Yes most clients resume but you didn't say what you are using. If a download is going too slow, stop that one and try another IP address. At 56K you should get files at 2K Bytes per second and above most times, if you download two at the same time from two different places it seems to work better speed wise.