Potentially Good but flawed
***Contains spoilers*** Quite frankly, I never truly hated this movie, I just never loved it either, and it's no doubt the weakest of the original series movies. Yes, I understand the project was snake bit on many levels, but most Trek fans know that Star Trek was always more about quality story telling than it was about dazzling special effects and sci fi gimmickry. I thought it had some potential, and did include some good character scenes, interesting messages (even if Shatner cheesed up the moral about inner suffering), and had an ending that seemed to provide a set up for the superior Star Trek VI. So aside from my smaller problems (Sulu, Chekov, Uhura and Scotty largely being pushed to the background, the feeling of TMP Deja Vu on many levels, etc) here goes...
The Humor...Anyone who know me can tell you I love a good joke, and have a good sense of humor, but humor didn't work right in this film. Yes, humor works in Star Trek when done right, it worked in ST IV because they didn't go overboard with it, the humorous lines were consistent with the characters, and much of the humor fit in with the culture shock of traveling 300 years in the past. Here it almost seems forced with one one liner after another, and many of the comedic scenes would have worked better if depicted more straight forward such as...
Sybok...I really think he wold have been accepted better if he was handled more differently, it didn't help that the revelation of his being Spock's brother was depicted almost as an Abbott and Cotello routine between Kirk and Spock. And Kirk, never knew the closet thing to a best friend he had never had a brother, it's one thing not to know wether, say, a second year Ensign under your command was an only child or not. When Kirk confronts his closet confidante about it, Spock just gives a cop out answer about not seeing the logic to say anything sooner. The could've maybe been some reference to some past off screen revelation (ie "Jim, remember me telling you about my estranged half brother..."). It's even possible McCoy would've at least have had some knowledge of Sybok after carrying Spock's Katra. Also, we have this revelation about Sarek, a well known (and beloved) supporting character, we want to know more about this past marriage to a Vulcan Princess (perhaps it was her he had pon farred with, and it was her death or their separation or divorce that lead to him marrying a human woman), but we'll never know because they cut to the chase, and all is forgotten and no one thinks to follow it up.
Klaa...This had to be the weakest commander in the history of the Klingon Empire...He goes after Kirk merely because he was bored, come on! Certainly it would have made more sense if he was a Klingon who had a personal vendetta against Kirk (redundant I know), or was some truly blood thirsty Klingon ( perhaps some sort of Klingon Bounty Hunter) heeding the words of the Klingon Ambassador's call for Kirk's head in ST IV. Then when captured is shamed by a disgraced General to apologize, hardly the actions of a true Klingon.
Finally, the God creature...Was it God they met, Satan perhaps, or some evil alien entity appearing as a God figure? We never know, I suppose that was the intent, that it was supposed to be left up to viewers interpretation, but left too little awes or clues to do so satisfactory.