I will qualify my review by first stating that I would NOT be considered a fan of Sherlock Holmes. Other than this movie, I've never watched any of the series on TV, nor do I believe that I have ever read any of the Sherlock Holmes books. Overall, I just found this movie to be very entertaining, with a good story, some good acting, and good special effects. Surprisingly, my 9 year old daughter sat down mid-way through the movie, and stated how much she liked it. So, we went back and watched the whole thing again, and at the end her comment was, "I LOVE THIS MOVIE!" So, we're very much looking forward to watching the sequel in the very near future.
All that said, if you are a hardcore Sherlock Holmes fan, you MAY not enjoy this movie as much as we did. As I said, I am NOT a die hard Sherlock Holmes fan, but I had a couple of friends of mine comment that they didn't really like this movie, but recommended the BBC series instead (also available on Amazon On Demand). So, I have a feeling the movie may stray a bit from the classic Sherlock Holmes. So, I am now also going to check out the BBC series as well, but I wouldn't let those comments dissuade you from checking this movie out.
As a note - this is a movie probably best watched in a dark room with the sound turned up. There are quite a few dark scenes in the movie, and it can be a bit difficult to see in a brightly lit room. In addition, the characters also whisper / talk under their breath more than usual in a movie. So, if you're not prepared for that, you may miss what they're saying (some of which is particularly entertaining), especially with British accents.