I liked TFF, mainly because I read the novelization first and loved it. But looking back, I guess it didn't make much sense that this super powerful entity needed a starship or that it only communicated with Sybok. Surely there are other Vulcans and even more telepathic species out there. Perhaps they should've changed what the entity wanted. Perhaps there should've been a community of different species, 'believers' already down on the planet and the entity was using their belief in it to power itself, something like the Ori from Stargate SG-1.
I wouldn't have minded Sybok being a little more fanatic-if pressed- and manipulative. Also, I would've liked to see what pain the other crew members had besides Spock and Bones.
I read once that the plan had been to use the Romulans instead of Klaa, and I wish they had gone with that. It would've been nice to see an updated Romulan warbird in a TOS
Also have better FX.