Truly awful, perhaps in order to better suit the movie. William Shatner and daughter - who is with him for having written a book about the making of the movie, as well as worked on it as some kind of assistant to her father - pretty much waste the opportunity to explain the circumstances under which he ended up being the perpetrator of the worst Star Trek movie ever made (only during the "live flashbacks" scene he quickly mentions that "this is how I imagined the movie would be"). Actually, they fail to explain anything at all, such as why the filmmakers replaced Industrial Light & Magic visual effects for Z-grade ones. The entire commentary is about random digressions regarding lighting, the size of the sets and how tight the budget and schedule were.
To be fair, there was an interesting bit: when he tells the insatisfaction DeForest Kelley had about a scene because it required his character to do something morally questionable.