It might be usefull for Cyberduck to have a preference setting to limit the upload speed (and maybe download too).

My cable connection gives me approximately 1 mbit/s download speed but only a meager 192 kbps upload. Many broadband connections are capped in a similar way.

Anyway, using Cyberduck to upload a large file (movie, + 40 MB) to my website will cause all other traffic to stall because Cyberduck will use all upload capability available. If I could instruct CyberDuck to use no more than 100 kpbs for uploading, my upload will last somewhat longer but main internet usage won't be disturbed much.