I have used it thru Canoo sometime back.
But had a hard time convincing the management on its usefullness.
HTMLTidy forces strict DOM standards which IE doesent follow. If theres a missing tag for example - IE still processes it. And since nothing was *actually* wrong with the page - no errors the developers used to ignore these errors.
It took a long time to convince the management on its effectiveness - nevertheless a great tool! I wish I ahd come to know about it when I used to have problem in object recognition with other tools - I bet a lot of them would get solved this way.