Being able to give rare files priority would be nice
 

When there are 20 people trying to get a popular file and 1 trying to get a rare file. I would like the option to give the rare file priority over the popular file

Some kind of rating system for the shared folders, so you could have rare files in one and popular files in the other. Also small files should be allowed to download before big files to some extent

Or being able to right-click a file in the upload window and press priority, and then another download temporarily pauses while it's being uploaded

I will give that my vote