This is a stylish Sherlock Holmes film with the best foggy-London atmosphere I've ever seen on film - just great photography with some wonderful, murky shots. I saw it on VHS and I wouldn't mind seeing it now that it is available on DVD. It has to look really good.
Unfortunately, the story doesn't match the cinematography. It just bogs down in too many spots. The script could have used some better editing. It's hard to watch for more than an hour without your mind wandering.
Christopher Plummer and James Mason make a good Holmes-Dr. Watson pair, respectively, with good chemistry. I could have done without all the religious exclamations spoken by Mason. A little too much credence is given the "medium" (Donald Sutherland) too, but filmmakers have always loved promoting the occult, especially in Britain, land of "Harry Potter." Sutherland's role was minor (but played up by critics, of course.) As another reviewer pointed out here, you'd never see a character like that show himself in a Conan Doyle piece of literature.
The ending is typical modern-day film-making in which the government is corrupt and the Free Masons are the bigoted villains. I'll stick with Basiil Rathbone versions of Sherlock Holmes where you don't have all the political agendas and they concentrated on just telling the crime story.