Removing software that came from a pkg file?
Not a direct answer to your question, but you can also use "Suspicious Package", a QuickLook plug-in for Finder, to see what files a package installed: http://www.mothersruin.com/software/SuspiciousPackage/

Depending on what files were installed where, you may be able to find them in Finder and drag to the trash; otherwise you may have to go into Terminal and rm around.