Not nearly as cult, gross, bad or ridiculous as the hype around it. And way funnier.

Production and actor are better than a typical Z movie. Though past a certain point, there's not much acting going on. But the mad scientist nails it.

Nothing much is shown, so it's not even that disgusting or disturbing, I've seen much worse in this kind of movies.

However, apart from the basic idea, (well yeah, that's pretty original, you gotta give credit), they haven't really thought anything out.
There's a scene where they're shown painfully going upstairs. However at this point in the movie they've been repeatedly show inside/outside, upstairs/downstairs, even on an operating table. So how did they move all these times ? I don't think the doctor carried them on his shoulders.

As often in this genre, they had to often be really really stupid in order not to escape. I mean, come on, [spoiler]having a scalpel, stabbing the bad guy, and not even finishing him ? It's not like they could run to escape, they knew it would be long and difficult, much more than what hurting his leg a little would provide. And abandoning the scalpel ? Worse, when the doctor was crawking, the japanese guy had a lamp that was enough to smash him. But no, let's just give up and kill himself (should have also kept the scalpel for that), and well, too bad for the girls behind.[/spoiler]
Or even before the operation, [spoiler]I get she didn't want to leave her friend behind, but what did she think she could do dragging her around ?[/spoiler]

So yeah, past a certain point it was mostly frustratingly stupid. The doctor and his obsession added an unexpected effective dose of humor. The ending might have been the most disturbing point ([spoiler]what will happen to the middle girl, she really can't do anything sewed to two dead bodies[/spoiler]), but the situation makes it almost easy ([spoiler]two cops came there, in urgency, with a warrant. When there's no news from them, she probably won't have to wait more than an hour before help arrives.[/spoiler]).