i gave this a quick try and ... it wasn't so quick. however, performance was not horrible - especially for smaller or less complex documents.
just some ideas from a 10k ft view:
possible places to look(?) -
(1) Format of the HTML report(s) you're reading
JEditorpane - from what i can see - has about 15 html handling bugs
being fixed in 1.5, including an important-looking META tag support bug.
API gives current HTML support at 3.2 (if in doubt, report
compliance could be verified w tool like jtidy also see last item below)
(2) issues related to _read (vs. using constructor or _setPage)
(a) *non* asynch vs asynch performance; (b) existence of
relative path refs (determination of basedir), (c) content type, etc.
(3) content itself
can be set/checked before/after instantiation.
any possibility of charset issues? is doc editable?
finally, there's a
jeditorpane-based simple browser (platespiller ) out there that you could use as a baseline - to see if these reports display ok using that browser, and to check the rendering integrity and performance deltas
hth - good luck!