If people are getting really slow uploads from you, you can try reducing your number of upload slots & number of simultaneous uploads per host. Or maybe play around with your upload bandwidth. This thread has lots of tips for setting up LW well
http://www.gnutellaforums.com/open-discussion-topics/27036-few-things-consider-while-configuring-limewire-optimal-performance.html

this too
http://www.gnutellaforums.com/download-upload-problems/17321-maximizing-upload-download-success-limewire.html