As a kid*, it was wonderful.
There was a neat mystery setup.
And it was so different in tone and style to III!
It continues from III, complete with using a clip of the previous movie as a recap and back then discussions of "How'd they get that pristine footage!" didn't exist with such fervor... of course, home video playback equipment - while existing - hadn't reached its zeitgeist yet and many movies were expensive. That and the Atari 2600 and Nintendo Entertainment System made kids' lives more interactive. I never really got into the NES at the time, and how come chocolate ice cream doesn't come with the model that doesn't come with the new car? Wait, what were we talking about again, ice houses with propellers that fly around like jet planets?
Everyone, however, prior to its release, was joking with cracks harking back to Doctor Who (back when it was geared to nerds) and even Back to the Future.
The humor contained in the 20th century was fantastic.
Right down to primitive medicine and, of course, Noocular Wessons in Awwameadah.
I wanted to save the whales but didn't live near a beach.
At the time, it was fresh and new and crisp and wonderful to see the heroes back in it for an all new adventure after reruns of TOS and the movies.
Nowadays, it's not quite the same experience...
The movie kept the humor contained for the 20th century Earth scenes and didn't splatter it across the 23rd. A sage move... unfortunately every subsequent Trek movie feels a need to poke jokes, even at character expense, and it doesn't work. Often because it's aimed at the audience than feeling integral to or flowing within the story.
The end credits rank up there with a cheesy sitcom's.
So does the incidental music.
And somewhere between drafts the number of charges dropped by a considerable margin for no reason.
The only thing from the flick that has somehow aged well is the entertaining yet nihilistic-themed punk song.
And the LDS joke. That one's timeless, even though today's junkies have never tasted the original flavor - or even the modern day varieties - of Grace Slick's favorite hallucinogen, which she almost got a chance to spike Nixon's tea with (for real!

) But a lot of jokes don't hold up at all. Some do to a good extent, others not so much. If nothing else, the "Not now Madeline!" makes a sort of sense, but they should have gotten Wayne Knight instead. He was a blast in FOX's ill-fated-despite-being-genuinely-witty-which-was-a-rarity-at-the-time sketch show "The Edge"...
But the whale effects still look great... I bet they had a whale of a time making them... unfortunately the plot is undeniably heavyhanded, as if they were slamming us on our heads with Free Willy's tail fin, the fin and the audience were proportionally sized... As if the audience could do anything except put nickels into those glorified specimen jars of which a tiny fraction went to some guy on a boat that farmed cuttlefish and that was that. If nothing else, sledgehammer tactics didn't start in the 21st century.
* trying not to date myself too much, I'm celibate by choice...