Like the other posts have mentioned: the video quality is decidedly poor. It seems to have been taken from a videotape source due to the numerous drop outs that are evident througout. Still, it's by far the best version available (aka Nightmare Castle on other low-quality labels) and it's far from unwatchable and even fairly crisp in spots. The audio is okay, the dubbed dialogue is clear even if there's a slight hiss to it.
As for the film... it's a blast! This is my favorite Barbara Steele performance and she plays two roles: the insatiable, insane, raven-haired Muriel and the demure, blonde and driven insane Jenny. The whole thing's encased in a fog-thick atmosphere of dread, sadism and passion that even outdoes many of the Corman/Poe adaptions. Witness the doctor's torture of Muriel and her lover and then Muriel's gleeful climactic revenge. Pretty powerful stuff even by today's standards... and although it's draggy in spots it has many memorable scenes that make it worthwhile.
The print's uncut and 100 min. It's incorrectly framed at what looks like 1.50:1 instead of 1.66:1 and the first couple of credit titles are video generated. There also seems to be some new sound efx of crickets and such added over the first scene for some inexplicable reason.
The box cover art is hideously wretched (doesn't Retromedia have a designer that knows rudimentary Photoshop?). The slightly animated menus are passable as is a small photo gallery set to Ennio Morricone's cool theme.
Again, the quality should have been better but if you can score it for $... so (and you're a fan) than it's definitely worth it... until a superior version comes along.