While this Sherlock story will probably appeal to families with older kids, the hardcore Sherlock fan will be appalled. As mentioned in other reviews, the villainess shares the name of a beloved character from the Sherlock stories, but none of her marvelous traits. Furthermore, Jonathan Pryce, while a fine actor, seems very out of character for Sherlock, seeming much too like a sweet older gentleman than the proud, somewhat aloof Holmes.
The action focuses on the Irregulars and the story seems to try to pander to a young audience with this crew. Unfortunately, for the first half of the story, I found it difficult to have much interest in them. By the second half, as I accepted the movie for what it was, I did find some humor and charm in it.
As mentioned by others, there are some really good lines. There's also some really intriguing camera work that reminded me of some of the more experimental moments in the Granada series (like in the Devil's Foot, for instance) and a good soundtrack.
When I was able to pretend it wasn't supposed to be a Sherlock Holmes story, I enjoyed it as much as I'd enjoy most movies geared towards a tween audience. But I don't intend to ever watch it again.