You remember quite correctly--ACD's Watson was not at all bumbling. He was the one telling us the stories, after all! But as soon as they started making filmed versions, they went to bumbling--think Basil Rathbone's Watson in particular. The Granada Watson was reasonably intelligent, and I find this version of Watson someone who, as in the ACD stories, can't keep up with Sherlock deductively speaking, but is intelligent and highly competent in his own right.