Without Ian McKellen's acting, this film may not have been quite as enjoyable. If any other actor spend 60% of the time lying in a bed and reminiscing on past memories, I probably would have gotten bored at the half hour mark. Somehow, even at age 76 McKellen is capable of being Sherlock Holmes. Of course, he portrays the annoyingly witty side of Sherlock, but also masters the compassionate side of the character.
The one part of this film that felt wrong to me was the timeline. Of course, Sherlock Holmes films are going to be a bit cluttered to reveal the mysteries involved. Yet this one just felt a bit too cluttered. The scene jumps from past to present so oddly that I felt lost after a while. Aside from the time jumps, there are three different stories going on at once (one involving Japan, one involving a woman from Holmes's past, and one involving Sherlock's caretakers). The film has interesting mysteries, yet they all collide towards the end creating a material mesh.
The Bottom Line: This film brings a new look at Sherlock Holmes as an aging man played by the ever-so-great Ian McKellen, yet comes out a bit jumbled towards the end.