Cannot, will not, and have never been told any reason I should. In fact, it would be like letting someone shit in my eyes, I'm told.
All I ever saw was a clip with the Invisible Man explaining his invisible life, not a word of which came from Moore, not a bit of which showed the characterization that makes him a worthwhile character, just about showing off the effect. That was enough to ensure I'd never look.
FROM HELL pissed me off most not just because it's just another Jack the Ripper movie that they just used Moore's title on. But even more insultingly, I had said many times that based on Campbell's drawings, Robbie Coltrane should be Abberline. Not only was he not, they made him Depp's SIDEKICK. Also, the movie made me start to dislike Johnny Depp. It was a lazy performance and his character didn't make any sense. I can accept that a movie has to have changes(I like Kubrick's THE SHINING better than King's, and thank god the film of the Godfather ISN'T like the book), but not ones that violate the heart of what you're adapting.
Or you could be like WATCHMEN, and be incredibly faithful and still miss the whole point.