Although this cant really be set completely right unless limewire changes a bit, the uploads can be configured according to how fast you want a user to be able to connect.
Say you have tons of movies, you might want to dedicate uploads to few people, so they can upload at a faster rate.
Or if you had only music files you might want to allow more users to connect.
This way, a user doesnt have to try to upload one movie for weeks, that she can do it in a matter of days. Because music files are smaller, giving less bandwidth per user doesnt really matter as much, becuase uploading at 1KB/s may be annoying, but it wont take weeks.
I have mine set (I have lots of video files) so that if the maximum number of users allowed connect, they can have 8KB/s, assuming of course they can handle that.