As a fan of what Rob Zombie tries to do, I can understand that his movies tend to fall apart toward the end.
Everything about this movie made me think of Texas Chainsaw, which I suppose was the intention. It made it a little weak in my opinion though, there was a lot of potential that, with this being Rob's first film, I feel missed the mark.
As with a lot of his media, Rob Zombie has a really uncomfortable sexual undertone to his movies. I understand that's an element that horror tends to employ, but I feel Rob does it a little heavy handed.
And Doctor Satan? Really? Nice name dude.
Worth watching for the knowledge of having seen it, but I wouldn't see it twice.