TFF and TMP are my two favorite Trek films. TMP is a cinematic masterpiece. Yes, the plot is clunky and slow, but the cinematography reached an epic artistic scope that non of the other films could emulate. ST09 was really the first one that came close.
TFF is just so ridiculously absurd, it's hard not to love it. I think a lot of fans cringe and stick their noses up at it because they perceive themselves "above" the humor. The problem is, they're so busy rolling their eyes at the slapstick, that they miss some of the exceptionally well-place wit of the dialog.