Rupert Everett, who has an impressive film resume, was unfortunately miscast as Holmes. It's not that Evrett is too pretty or anything, it's just that his chisled face was too immobile, and his attitude too enervated. He lacked Rathbone's energy or Brett's edge. Ian Hart, who had previously played Watson in a 2002 adaptation of the "Hound of the Baskervilles" (Richard Roxburgh as Holmes--haven't seen it--) was a much better Watson. In fact, it could be argued that Watson is the real protagonist of this story, not just because he is first on stage.
This would have had to be one of those stories that had resided in the famous dispatch box in Charing Cross, since the sexual theme (including the indiscretion of a great lady) would not have been publishable in "Watson's" day. However, the events of the story are not beyond something that could have happened or conceivable been part of a Holmes' case. However,as feared, the writers did take liberties with the Holmes canon, some admirable and some not. On the NOT side, Holmes is shown in the very opening sequence smoking opium, a vice I don't believe he ever indulged for recreation. He is also portrayed as using cocaine while a case is in hand, something antithetical to the Holmes we know. In mitigation it must be said that the reason for this extreme behavior is partly due to Watson's moving out on Holmes in order to be married which casues stress between them that is otherwise well-played out. The writers took an imaginative approach to the "problem of the second Mrs. Watson,"* by having her be a medical woman and an alienist (they actually use the more modern term "psychiatrist" which I don't believe was in use in Holmes' day), which actually gives her a small part to play in the resolution of the mystery. Unfortunately, the part is very small, since, when called upon, Holmes can give a psychological breakdown on the criminal that would do any modern "profiler" proud.
Viewed as a Victorian mystery alone, it wasn't absolutely dreadful, although there are some significant plot holes viewed retrospectively. Amusing, if just to pick apart. Brett's laurels are in no danger.
*For those who are not Sherlockians, the identity of the second Mrs. Watson is one of the great unsolved mysteries of the Holmes canon. After an initial batchelor phase of rooming with Holmes, Watson married Mary Morstan, the heroine of "The Sign of the Four." Although we are never told why, Watson is widowed and moves back in with Holmes. In later stories, Watson again makes reference to having a wife, but her name or the circumstances of his presumed second marriage are never given.