-- You're quite right though, there's no escaping the fact that he wasn't really Herbert's baron.
But when I saw the movie, Lynch's Dune, my reaction to Baron Harkonnen was visceral and emotional. Lynch did a fantastic job of communicating in just a few scenes how morally bankrupt and, not to put too fine a point on it, Eveeell, the Baron was. THAT was totally consistent with Herbert's books, the Harkonnen name was still a shorthand for degeneracy thousands of years later.
For me it was the movie and then the books. The tone and feeling of the books made it to the screen in Lynch's version. These were totally absent from the modern movie versions (I was so pissed at it, I started yelling at the screen after 5 minutes and had to stop watching after 10).
The sonic doo-hickey was a movie shorthand for Paul's (via his mother and superior trainers) martial skill. Plus, it looked good.
I don't fault Lynch, he did a good job of converting a very dense book to the screen and delivering enough emotional impact that I read the books and am still talking about them 25 years later.