You can set files to be powershared by right clicking them in the shared files list and selecting "Powershare" -> "Set powersharing". Files that have powershare activated will be uploaded a 100% of the time, if there are people trying to download them. It doesn't matter how many other files you share or download. This makes it possible for you to release files efficiently, and still download files normally. If the files with release priority doesn't use all the bandwidth, normal shared files are uploaded. This means that you won't have to unshare everything that you are not releasing. This gives more sources for files on the network, and make sure the allotted upload bandwidth are always used a 100% efficiently to release your files.
Post questions about this feature in this thread.