Whatever it must have been like being a co-star of Shatner's, I do distinctly remember all of the TOS cast saying that being DIRECTED by him, in ST V, was completely different. Strictly as a director, he was totally professional and treated the entire cast with 100% respect. There was none of the baggage that came with being a fellow *actor* during the original series.
My wife and I were at a convention two weeks ago in San Francisco. Both George Takei and Walter Koenig were there.
Both took time to comment on Shatner (as they usually do). But Koenig did in fact say that as the director of ST:V, Shatner was great.
In fact he did a little impression of him:
"Walter...that..........was GOOD!"

), which I believe was illustrating American industrial/technical innovation in the present (and he would announce he was portraying a character relevant to the subject), with references/dramas about the same in the nation's early years. He was to the point, but could be dramatic when required whether on camera, or narrating scenes talking about the early America's struggles.