The original (Gygax/1E) version was an infamous party killer. Each subsequent revision nerfed it down by small increments. I fear the 5E version will be about as threatening as mini-golf.
I owned the original, but it was one of the very few modules I never bothered with - it really was designed as a DM vs PCs scenario, and I didn't care for that. Its my job to entertain my players, not make them miserable.
That being said, I was unaware that 5e was far enough along already to run entire campaigns. I stopped play-testing it some time ago. Perhaps I should have another look at it....
I have fond memories of KotB - I've used that quite a few times.
"I have never in my life learned anything from any man who agreed with me" --- Dudley Field Malone