Somehow I never before managed to watch the entire movie in the 43 years since it was released. Kieren McMullen sums it up well in his valuable book The Many Watsons: "The movie is, in a way, a little hard to get your mind around. It is not a spoof or a comedy and yet it is not completely drama."
I found it enjoyable, and yet unsettling in a way that all Holmes productions that go too far afield from the Canon are unsettling to me. Kieran notes that Robert Stephens underplays the role of Holmes in a way that makes him likeable. Indeed he is likeable, but he's not the frenetic Holmes that I know and love.
All the energy in this movie comes from Colin Blakely, who is surely the most excitable Watson that I can recall. And, as Kieren notes, he's a bit of a buffoon in the Nigel Bruce mold.
The central plot of this lavish production was actually a rather good mystery, I thought. But most of the first 20 minutes could have been cut to the film's advantage. And two major story lines of the movie were already cut to get it down to two hours.