He lambasted Star Trek V
back in 1989 and said some pretty biting and unflattering things about the film (but then it's difficult to find a critic who didn't) and I remember being taken aback at the time because it was the first Trek film he didn't like. In fact, he thought it was just plain terrible.
As time went by I came to recognize that most of his criticisms were valid and correct in spite of my personal attempts to make the fifth movie seem better than it was. Cheesy special effects: check. Villains (specifically the Klingons) you don't care about
: check. Secondary supporting characters who are introduced with a lot of dialogue and setup and then given nothing to do: check. Sloppy direction from Shatner: check.