I think that I used JDiff (http://javadiff.sourceforge.net) or something similar a while ago (unrelated to Pivot) to try to identify important API changes.
Pivot source is available anonymously, so anybody is free grab the source for a pair of tags and use a tool such as JDiff for their own purposes. http://pivot.apache.org/svn.html http://svn.apache.org/repos/asf/pivot/tags/
