In some ways, Star Trek V: The Final Frontier is an ambitious movie pretending to be popcorn entertainment pretending to be an ambitious movie. There's a lot of nonsense about self-help, not to mention the whole God thing, and none of it works. Partially, it doesn't work because David Loughery's script is too thin, but it also doesn't work because Final Frontier is paced as an action movie, not a self-reflective sci-fi outing.
But there's a definite subtext–not quite subplot, the film ignores any subplots it starts–regarding the continued bond between William Shatner, Leonard Nimoy and DeForest Kelley. About the only thing the movie does really well is the character stuff, not just for those three principals (it's often a comedy showcase for Kelley), but also for the rest of the regular cast. Of course, the script forgets about developing these good character moments, but they're nice to have around.
There's also a good performance from Laurence Luckinbill as the film's de facto antagonist. The handling of his character is another positive about the film. He gets more of a character arc than any of the regular cast.
As far as directing, Shatner does a fine enough job. The action's fast-paced, with excellent editing from Peter E. Berger. Andrew Laszlo's photography is decent too. A lot of the special effects are fantastic. Except the end when it really needs them.
The Jerry Goldsmith score's trying.
The Final Frontier's about as good as any "Star Trek finds God" picture could be.