rpm has 2 nice functions which let you - given a package, know what files will be / are installed - given a file, know to which package it belongs I miss them in portage.
You do not know which files are installed until after you build the package. So you cannot have that list until you build it. qpkg -f <--- Installed files and who owns them. There are other bugs relating so more specific requests on this line.
Sorry, I did not know about qpkg. It looks just great. By the way, emerge -s qpkg does not report anything, which is not very helpful.
gentoolkit