Having seen "Sherlock Holmes" a second time, I feel more compelled to comment on the martial arts presented in the film.
In the Sherlock Holmes story "The Adventure of the Empty House" (1901), Sir Arthur Conan Doyle writes about Holmes's martial arts knowledge by having him refer to "baritsu, or the Japanese system of wrestling".
However, there is not and never has been any real martial art named "baritsu". The name is in fact based on a British martial system named Bartitsu. This style was developed at the turn of the last century by E.W. Barton-Wright. Barton-Wright had spent some time in Japan and learned a bit of Jujitsu and Judo. He was also an exponent of stick fighting, boxing, and Savate. Because of his wide knowledge base, Barton-Wright is considered to be far ahead of his time in terms of mixing martial arts styles in order to create a more effective fighting system (however, it should be remembered that there was a time before systematization ruled, and the old masters were knowledgeable in all basic martial concepts).
While in the film Downey's character does demonstrate a variety of martial capabilities, the word "baritsu" is never mentioned, and the fighting style the great detective utilizes appears to be much more akin to Wing Chun than anything else (in fact, a Wing Chun wooden dummy can be seen in the apartment at 221b Baker Street). This is most likely due to Robert Downey, Jr.'s real-life practice of the Chinese style. Downey likes to mention and demonstrate his love for the system to many interviewers, and he even gives his martial arts practice some credit for his recovery from drug addiction.
Holmes uses similar poses and the vertical fist espoused in Wing Chun. To be fair, though, he also uses some Jujitsu, boxing, stick fighting, and all-around dirty fighting. His fighting ability comes in quite handy when doing battle with the criminal element. He also likes to blow off steam and practice his technique by participating in bare-knuckle fights at a bar called the Punchbowl.
Jude Law's Dr. John Watson fights rather differently, however. While Holmes takes some time to mentally calculate his strikes and their damages, Watson just goes at it. He just hits anyone and everyone with anything in reach, including but not limited to his sword-cane. This could be because Watson is not such a calculating fellow, and is an ex-soldier (in my personal experience, military men tend to brawl rather than calculate).
The fights are interesting and fun to watch in the film. I think that they demonstrate a great blend of Sir Arthur Conan Doyle's writings, director Guy Ritchie's love of Karate and Jujitsu, Robert Downey, Jr.'s love of Wing Chun, and just plain good characterization and visual acumen.