Question re: setting the upload slider to 100%

If I set it to 100% (or unlimited), does that hinder my download speeds? I sure don't want to slow them anymore than they are.

I currently have my uploads set to around 50% (25 kb/s). What I didn't realize was that it was shared between all uploads. Or, at least, it seems to be.

I am on a Cable modem and my downloads run on average at about 10 kb/s. Very few will run over that. And even more rare are the ones over 100 kb/s.

So, back to the original point: What effect does my upload speed setting have on my download speed?

Thanks!