Wouldn't the torrenting world be so nice if everyone just let each other use all their bandwidth up Although I think its unlikely for that to happen, it does help having at the very least, a high UL limit. But I've definatley noticed that theres a point at which your not getting anything in return for what your uploading so its wise to set a limit.
btw: Downloading at 20-30kb/s is waay better than what many people face every week.....
Actually No. Setting your upload to no limit isnt the way to do it. Thats only if you're seeding, if you want to be able to download at all, you HAVE to set a % limit on your upload, else it chokes your download.