For my money, you can't really go wrong with Robert Downey Jr. or Rachel McAdams and I mostly always like Jude Law and in this picture they were all great fun to watch. While the thought of Holmes and Watson being so ass-kickingly awesome seems a bit of a departure from how I'd always interpreted the Conan-Doyle characters, it succeeded in bringing these 19th century English blokes to a 21st century audience that likes their heroes to be well versed in taking and throwing punches.
On the other hand, I had thought that part of what made Holmes and Watson great was that they simply out-smarted rather than out-fought the bad guys. This movie lets them do both and sometimes simultaneously. And I can't deny that I rather enjoyed seeing the friendly camaraderie between Downey and Law as well as the way that the movie played up Watson as more than a mere sidekick but rather a partner to Holmes.
In the end, the door was left wide open for a sequel as Professor Moriarty turned out to be the true scoundrel who escaped capture (not to mention that Holmes helped facilitate the eventual escape of Irene from custody), and if they do make another, I will surely see it.