Some do bring much. Those that don't should be improved. They should tell how the package fits into the whole of JSword, especially from an architectural design perspective. We've never gotten around to it because there is always something more interesting to work on.
I think that we should have a separate issue to update all the public Javadoc to be meaningful and proper.
Meaningful: The comment tells how the item fits into the class as a whole, not merely stating the obvious.
Proper: Every parameter, return, thrown exception, parameterized type is listed (and meaningful).
Having such will make it easier for new users to use JSword.
The value of migrating to the Java 5 form is that there are only .java files under src//java.