Well, thanks to Jon Favreau and Mark Steven Johnson, there's at least been a tendency among Hollywood auteurs to at least attempt to carry over the spirit of source material to major-budget movie adaptations. Favreau did a nice job with "Iron Man", The director's cut of "Daredevil" was nicely executed by Johnson and now add Guy Ritchie to the mix with "Sherlock Holmes".
It's not perfect, mind you. There are periodic slip-ups, some minor character alterations, but the spirit is there. The mysterious woman, Holmes' muse and frustration is here, and carried well by Rachel McAdams. LeStrade is the numb-skulled, but well intentioned chief inspector of Scotland Yard. These translated well. One would expect a bit older an more portly Dr. Watson than Jude Law, but as I said, in Hollywood, compromises are made, and Law's excellent humor and physical presence more than makes up for the tangible differences.
Downey amazes me. When you consider the shitstorm his life and career had become, and look at his work since his comeback, (which actually began with the spectacular "Kiss Kiss Bang Bang", if you haven't seen it, get on it) he's priceless. He holds the accent through the film, carries over Holmes' substance abuse, martial arts expertise, musical prowess, and yes, the defining characteristic, deductive reasoning. To the point where it becomes a physical nuisance, an exhaustive hypersensitivity to his surroundings. Interesting and overlooked touch from Doyle.
I'm not going to go into the plot, it's complicated and I don't want to spoil. Those hoping for classic Guy Ritchie touches in the visual arena won't be disappointed. Choreography, film speed, limited but acceptable CGI usage, and humor are all vividly and properly installed here.
This is a good film, well thought out and acted, and helmed by a confident director. Whether you've read Doyle or not, you will enjoy it. Frequent readers, as myself, will find themselves performing knowing nods and grins throughout.
That's all you can ask for in a modern Hollywood film.